The Collaborative International Dictionary of English v.0.48:

Strain \Strain\, v. t. [imp. & p. p. Strained; p. pr. & vb. n.
   Straining.] [OF. estraindre, estreindre, F. ['e]treindre,
   L. stringere to draw or bind tight; probably akin to Gr. ? a
   halter, ? that which is squeezwd out, a drop, or perhaps to
   E. strike. Cf. Strangle, Strike, Constrain, District,
   Strait, a. Stress, Strict, Stringent.]
   1. To draw with force; to extend with great effort; to
      stretch; as, to strain a rope; to strain the shrouds of a
      ship; to strain the cords of a musical instrument. "To
      strain his fetters with a stricter care." --Dryden.
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   2. (Mech.) To act upon, in any way, so as to cause change of
      form or volume, as forces on a beam to bend it.
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   3. To exert to the utmost; to ply vigorously.
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            He sweats,
            Strains his young nerves.             --Shak.
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            They strain their warbling throats
            To welcome in the spring.             --Dryden.
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   4. To stretch beyond its proper limit; to do violence to, in
      the matter of intent or meaning; as, to strain the law in
      order to convict an accused person.
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            There can be no other meaning in this expression,
            however some may pretend to strain it. --Swift.
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   5. To injure by drawing, stretching, or the exertion of
      force; as, the gale strained the timbers of the ship.
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   6. To injure in the muscles or joints by causing to make too
      strong an effort; to harm by overexertion; to sprain; as,
      to strain a horse by overloading; to strain the wrist; to
      strain a muscle.
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            Prudes decayed about may track,
            Strain their necks with looking back. --Swift.
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   7. To squeeze; to press closely.
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            Evander with a close embrace
            Strained his departing friend.        --Dryden.
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   8. To make uneasy or unnatural; to produce with apparent
      effort; to force; to constrain.
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            He talks and plays with Fatima, but his mirth
            Is forced and strained.               --Denham.
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            The quality of mercy is not strained. --Shak.
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   9. To urge with importunity; to press; as, to strain a
      petition or invitation.
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            Note, if your lady strain his entertainment. --Shak.
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   10. To press, or cause to pass, through a strainer, as
       through a screen, a cloth, or some porous substance; to
       purify, or separate from extraneous or solid matter, by
       filtration; to filter; as, to strain milk through cloth.
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   To strain a point, to make a special effort; especially, to
      do a degree of violence to some principle or to one's own
      feelings.

   To strain courtesy, to go beyond what courtesy requires; to
      insist somewhat too much upon the precedence of others; --
      often used ironically. --Shak.
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The Collaborative International Dictionary of English v.0.48:

Strain \Strain\, n. [See Strene.]
   1. Race; stock; generation; descent; family.
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            He is of a noble strain.              --Shak.
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            With animals and plants a cross between different
            varieties, or between individuals of the same
            variety but of another strain, gives vigor and
            fertility to the offspring.           --Darwin.
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   2. Hereditary character, quality, or disposition.
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            Intemperance and lust breed diseases, which,
            propogated, spoil the strain of nation. --Tillotson.
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   3. Rank; a sort. "The common strain." --Dryden.
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   4. (Hort.) A cultural subvariety that is only slightly
      differentiated.
      [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Strain \Strain\, n.
   1. The act of straining, or the state of being strained.
      Specifically:
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      (a) A violent effort; an excessive and hurtful exertion or
          tension, as of the muscles; as, he lifted the weight
          with a strain; the strain upon a ship's rigging in a
          gale; also, the hurt or injury resulting; a sprain.
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                Whether any poet of our country since
                Shakespeare has exerted a greater variety of
                powers with less strain and less ostentation.
                                                  --Landor.
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                Credit is gained by custom, and seldom recovers
                a strain.                         --Sir W.
                                                  Temple.
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      (b) (Mech. Physics) A change of form or dimensions of a
          solid or liquid mass, produced by a stress. --Rankine.
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   2. (Mus.) A portion of music divided off by a double bar; a
      complete musical period or sentence; a movement, or any
      rounded subdivision of a movement.
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            Their heavenly harps a lower strain began. --Dryden.
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   3. Any sustained note or movement; a song; a distinct portion
      of an ode or other poem; also, the pervading note, or
      burden, of a song, poem, oration, book, etc.; theme;
      motive; manner; style; also, a course of action or
      conduct; as, he spoke in a noble strain; there was a
      strain of woe in his story; a strain of trickery appears
      in his career. "A strain of gallantry." --Sir W. Scott.
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            Such take too high a strain at first. --Bacon.
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            The genius and strain of the book of Proverbs.
                                                  --Tillotson.
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            It [Pilgrim's Progress] seems a novelty, and yet
            contains
            Nothing but sound and honest gospel strains.
                                                  --Bunyan.
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   4. Turn; tendency; inborn disposition. Cf. 1st Strain.
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            Because heretics have a strain of madness, he
            applied her with some corporal chastisements.
                                                  --Hayward.
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The Collaborative International Dictionary of English v.0.48:

Strain \Strain\ (str[=a]n), v. i.
   1. To make violent efforts. "Straining with too weak a wing."
      --Pope.
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            To build his fortune I will strain a little. --Shak.
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   2. To percolate; to be filtered; as, water straining through
      a sandy soil.
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WordNet (r) 3.0 (2006):

strain
    n 1: (physics) deformation of a physical body under the action
         of applied forces
    2: difficulty that causes worry or emotional tension; "she
       endured the stresses and strains of life"; "he presided over
       the economy during the period of the greatest stress and
       danger"- R.J.Samuelson [syn: stress, strain]
    3: a succession of notes forming a distinctive sequence; "she
       was humming an air from Beethoven" [syn: tune, melody,
       air, strain, melodic line, line, melodic phrase]
    4: (psychology) nervousness resulting from mental stress; "his
       responsibilities were a constant strain"; "the mental strain
       of staying alert hour after hour was too much for him" [syn:
       strain, mental strain, nervous strain]
    5: a special variety of domesticated animals within a species;
       "he experimented on a particular breed of white rats"; "he
       created a new strain of sheep" [syn: breed, strain,
       stock]
    6: (biology) a group of organisms within a species that differ
       in trivial ways from similar groups; "a new strain of
       microorganisms" [syn: form, variant, strain, var.]
    7: injury to a muscle (often caused by overuse); results in
       swelling and pain
    8: the general meaning or substance of an utterance; "although I
       disagreed with him I could follow the tenor of his argument"
       [syn: tenor, strain]
    9: an effortful attempt to attain a goal [syn: striving,
       nisus, pains, strain]
    10: an intense or violent exertion [syn: strain, straining]
    11: the act of singing; "with a shout and a song they marched up
        to the gates" [syn: song, strain]
    v 1: to exert much effort or energy; "straining our ears to
         hear" [syn: strive, reach, strain]
    2: test the limits of; "You are trying my patience!" [syn:
       try, strain, stress]
    3: use to the utmost; exert vigorously or to full capacity; "He
       really extended himself when he climbed Kilimanjaro"; "Don't
       strain your mind too much" [syn: strain, extend]
    4: separate by passing through a sieve or other straining device
       to separate out coarser elements; "sift the flour" [syn:
       sift, sieve, strain]
    5: cause to be tense and uneasy or nervous or anxious; "he got a
       phone call from his lawyer that tensed him up" [syn: tense,
       strain, tense up] [ant: loosen up, make relaxed,
       relax, unlax, unstrain, unwind]
    6: become stretched or tense or taut; "the bodybuilder's neck
       muscles tensed;" "the rope strained when the weight was
       attached" [syn: strain, tense]
    7: remove by passing through a filter; "filter out the
       impurities" [syn: filter, filtrate, strain, separate
       out, filter out]
    8: rub through a strainer or process in an electric blender;
       "puree the vegetables for the baby" [syn: puree, strain]
    9: alter the shape of (something) by stress; "His body was
       deformed by leprosy" [syn: deform, distort, strain]