The Collaborative International Dictionary of English v.0.48:

Severe \Se*vere"\, a. [Compar. Severer; superl. Severest.]
   [L. severus; perhaps akin to Gr. ??? awe, ??? revered, holy,
   solemn, Goth. swikns innocent, chaste: cf. F. s['e]v[`e]re.
   Cf. Asseverate, Persevere.]
   1. Serious in feeling or manner; sedate; grave; austere; not
      light, lively, or cheerful.
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            Your looks alter, as your subject does,
            From kind to fierce, from wanton to severe.
                                                  --Waller.
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   2. Very strict in judgment, discipline, or government; harsh;
      not mild or indulgent; rigorous; as, severe criticism;
      severe punishment. "Custody severe." --Milton.
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            Come! you are too severe a moraler.   --Shak.
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            Let your zeal, if it must be expressed in anger, be
            always more severe against thyself than against
            others.                               --Jer. Taylor.
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   3. Rigidly methodical, or adherent to rule or principle;
      exactly conformed to a standard; not allowing or employing
      unneccessary ornament, amplification, etc.; strict; --
      said of style, argument, etc. "Restrained by reason and
      severe principles." --Jer. Taylor.
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            The Latin, a most severe and compendious language.
                                                  --Dryden.
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   4. Sharp; afflictive; distressing; violent; extreme; as,
      severe pain, anguish, fortune; severe cold.
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   5. Difficult to be endured; exact; critical; rigorous; as, a
      severe test.
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   Syn: Strict; grave; austere; stern; morose; rigid; exact;
        rigorous; hard; rough; harsh; censorious; tart;
        acrimonious; sarcastic; satirical; cutting; biting;
        keen; bitter; cruel. See Strict.
        [1913 Webster] -- Se*vere"ly, adv. -- Se*vere"ness,
        n.
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WordNet (r) 3.0 (2006):

severeness
    n 1: used of the degree of something undesirable e.g. pain or
         weather [syn: badness, severity, severeness]
    2: something hard to endure; "the asperity of northern winters"
       [syn: asperity, grimness, hardship, rigor, rigour,
       severity, severeness, rigorousness, rigourousness]
    3: extreme plainness [syn: austereness, severity,
       severeness]
    4: excessive sternness; "severity of character"; "the harshness
       of his punishment was inhuman"; "the rigors of boot camp"
       [syn: severity, severeness, harshness, rigor,
       rigour, rigorousness, rigourousness, inclemency,
       hardness, stiffness]