The Collaborative International Dictionary of English v.0.48:

Half \Half\ (h[aum]f), a. [AS. healf, half, half; as a noun,
   half, side, part; akin to OS., OFries., & D. half, G. halb,
   Sw. half, Dan. halv, Icel. h[=a]lfr, Goth. halbs. Cf.
   Halve, Behalf.]
   1. Consisting of a moiety, or half; as, a half bushel; a half
      hour; a half dollar; a half view.
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   Note: The adjective and noun are often united to form a
         compound.
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   2. Consisting of some indefinite portion resembling a half;
      approximately a half, whether more or less; partial;
      imperfect; as, a half dream; half knowledge.
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            Assumed from thence a half consent.   --Tennyson.
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   Half ape (Zool.), a lemur.

   Half back. (Football) See under 2d Back.

   Half bent, the first notch, for the sear point to enter, in
      the tumbler of a gunlock; the halfcock notch.

   Half binding, a style of bookbinding in which only the back
      and corners are in leather.

   Half boarder, one who boards in part; specifically, a
      scholar at a boarding school who takes dinner only.

   Half-breadth plan (Shipbuilding), a horizontal plan of one
      half a vessel, divided lengthwise, showing the lines.

   Half cadence (Mus.), a cadence on the dominant.

   Half cap, a slight salute with the cap. [Obs.] --Shak.

   At half cock, the position of the cock of a gun when
      retained by the first notch.

   Half hitch, a sailor's knot in a rope; half of a clove
      hitch.

   Half hose, short stockings; socks.

   Half measure, an imperfect or weak line of action.

   Half note (Mus.), a minim, one half of a semibreve.

   Half pay, half of the wages or salary; reduced pay; as, an
      officer on half pay.

   Half price, half the ordinary price; or a price much
      reduced.

   Half round.
      (a) (Arch.) A molding of semicircular section.
      (b) (Mech.) Having one side flat and the other rounded; --
          said of a file.

   Half shift (Mus.), a position of the hand, between the open
      position and the first shift, in playing on the violin and
      kindred instruments. See Shift.

   Half step (Mus.), a semitone; the smallest difference of
      pitch or interval, used in music.

   Half tide, the time or state of the tide equally distant
      from ebb and flood.

   Half time, half the ordinary time for work or attendance;
      as, the half-time system.

   Half tint (Fine Arts), a middle or intermediate tint, as in
      drawing or painting. See Demitint.

   Half truth, a statement only partially true, or which gives
      only a part of the truth. --Mrs. Browning.

   Half year, the space of six months; one term of a school
      when there are two terms in a year.
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The Collaborative International Dictionary of English v.0.48:

Back \Back\ (b[a^]k), n. [AS. b[ae]c, bac; akin to Icel., Sw., &
   LG. bak, Dan. bag; cf. OHG. bahho ham, Skr. bhaj to turn,
   OSlav. b[=e]g[u^] flight. Cf. Bacon.]
   1. In human beings, the hinder part of the body, extending
      from the neck to the end of the spine; in other animals,
      that part of the body which corresponds most nearly to
      such part of a human being; as, the back of a horse, fish,
      or lobster.
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   2. An extended upper part, as of a mountain or ridge.
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            [The mountains] their broad bare backs upheave
            Into the clouds.                      --Milton.
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   3. The outward or upper part of a thing, as opposed to the
      inner or lower part; as, the back of the hand, the back of
      the foot, the back of a hand rail.
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            Methought Love pitying me, when he saw this,
            Gave me your hands, the backs and palms to kiss.
                                                  --Donne.
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   4. The part opposed to the front; the hinder or rear part of
      a thing; as, the back of a book; the back of an army; the
      back of a chimney.
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   5. The part opposite to, or most remote from, that which
      fronts the speaker or actor; or the part out of sight, or
      not generally seen; as, the back of an island, of a hill,
      or of a village.
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   6. The part of a cutting tool on the opposite side from its
      edge; as, the back of a knife, or of a saw.
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   7. A support or resource in reserve.
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            This project
            Should have a back or second, that might hold,
            If this should blast in proof.        --Shak.
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   8. (Naut.) The keel and keelson of a ship.
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   9. (Mining) The upper part of a lode, or the roof of a
      horizontal underground passage.
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   10. A garment for the back; hence, clothing. [Obs.]
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             A bak to walken inne by daylight.    --Chaucer.
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   Behind one's back, when one is absent; without one's
      knowledge; as, to ridicule a person behind his back.

   Full back, Half back, Quarter back (Football), players
      stationed behind those in the front line.

   To be on one's back or To lie on one's back, to be
      helpless.

   To put one's back up or to get one's back up, to assume
      an attitude of obstinate resistance (from the action of a
      cat when attacked). [Colloq.]

   To see the back of, to get rid of.

   To turn the back, to go away; to flee.

   To turn the back on one, to forsake or neglect him.
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