The Collaborative International Dictionary of English v.0.48:

Tense \Tense\, n. [OF. tens, properly, time, F. temps time,
   tense. See Temporal of time, and cf. Thing.] (Gram.)
   One of the forms which a verb takes by inflection or by
   adding auxiliary words, so as to indicate the time of the
   action or event signified; the modification which verbs
   undergo for the indication of time.
   [1913 Webster]

   Note: The primary simple tenses are three: those which
         express time past, present, and future; but these admit
         of modifications, which differ in different languages.
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tense \Tense\, a. [L. tensus, p. p. of tendere to stretch. See
   Tend to move, and cf. Toise.]
   Stretched tightly; strained to stiffness; rigid; not lax; as,
   a tense fiber.
   [1913 Webster]

         The temples were sunk, her forehead was tense, and a
         fatal paleness was upon her.             --Goldsmith.
   [1913 Webster] -- Tense"ly, adv. -- Tense"ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

tense
    adj 1: in or of a state of physical or nervous tension [ant:
           relaxed]
    2: pronounced with relatively tense tongue muscles (e.g., the
       vowel sound in `beat') [ant: lax]
    3: taut or rigid; stretched tight; "tense piano strings" [ant:
       lax]
    n 1: a grammatical category of verbs used to express
         distinctions of time
    v 1: become stretched or tense or taut; "the bodybuilder's neck
         muscles tensed;" "the rope strained when the weight was
         attached" [syn: strain, tense]
    2: increase the tension on; "alternately relax and tense your
       calf muscle"; "tense the rope manually before tensing the
       spring"
    3: become tense, nervous, or uneasy; "He tensed up when he saw
       his opponent enter the room" [syn: tense, tense up] [ant:
       decompress, loosen up, relax, slow down, unbend,
       unwind]
    4: 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]

The Free On-line Dictionary of Computing (19 January 2023):

tense

   Of programs, very clever and efficient.  A tense piece of code
   often got that way because it was highly bummed, but
   sometimes it was just based on a great idea.  A comment in a
   clever routine by Mike Kazar, once a grad-student hacker at
   CMU: "This routine is so tense it will bring tears to your
   eyes."  A tense programmer is one who produces tense code.

   [Jargon File]


The Jargon File (version 4.4.7, 29 Dec 2003):

tense
 adj.

    Of programs, very clever and efficient. A tense piece of code often got
    that way because it was highly tuned, but sometimes it was just based on a
    great idea. A comment in a clever routine by Mike Kazar, once a
    grad-student hacker at CMU: “This routine is so tense it will bring tears
    to your eyes.” A tense programmer is one who produces tense code.