The Collaborative International Dictionary of English v.0.48:

Interval \In"ter*val\, n. [L. intervallum; inter between +
   vallum a wall: cf. F. intervalle. See Wall.]
   [1913 Webster]
   1. A space between things; a void space intervening between
      any two objects; as, an interval between two houses or
      hills.
      [1913 Webster]

            'Twixt host and host but narrow space was left,
            A dreadful interval.                  --Milton.
      [1913 Webster]

   2. Space of time between any two points or events; as, the
      interval between the death of Charles I. of England, and
      the accession of Charles II.
      [1913 Webster]

   3. A brief space of time between the recurrence of similar
      conditions or states; as, the interval between paroxysms
      of pain; intervals of sanity or delirium.
      [1913 Webster]

   4. (Mus.) Difference in pitch between any two tones.
      [1913 Webster]

   At intervals, coming or happening with intervals between;
      now and then. "And Miriam watch'd and dozed at intervals."
      --Tennyson.

   Augmented interval (Mus.), an interval increased by half a
      step or half a tone. Interval

The Collaborative International Dictionary of English v.0.48:

Interval \In"ter*val\, Intervale \In"ter*vale\, n.
   A tract of low ground between hills, or along the banks of a
   stream, usually alluvial land, enriched by the overflowings
   of the river, or by fertilizing deposits of earth from the
   adjacent hills. Cf. Bottom, n., 7. [Local, U. S.]
   [1913 Webster]

         The woody intervale just beyond the marshy land. --The
                                                  Century.
   [1913 Webster]

WordNet (r) 3.0 (2006):

interval
    n 1: a definite length of time marked off by two instants [syn:
         time interval, interval]
    2: a set containing all points (or all real numbers) between two
       given endpoints
    3: the distance between things; "fragile items require
       separation and cushioning" [syn: interval, separation]
    4: the difference in pitch between two notes [syn: interval,
       musical interval]

Moby Thesaurus II by Grady Ward, 1.0:

185 Moby Thesaurus words for "interval":
   abeyance, amount, aperture, arrearage, breach, break, broaching,
   caesura, caliber, cavity, cease-fire, cessation, chasm, check,
   clearing, cleft, coffee break, comma, compass,
   consecutive intervals, crack, cut, day, day off, defalcation,
   defect, deficiency, deficit, degree, delay, diapason, diatessaron,
   diatonic interval, diatonic semitone, disclosure, discontinuity,
   distance, downtime, drop, enharmonic diesis, enharmonic interval,
   extent, fateful moment, fenestra, fifth, fissure, fistula,
   fontanel, foramen, fourth, gap, gape, gat, grade, gulf, half step,
   half time, half-time intermission, halftone, height, hesitation,
   hiatus, hole, holiday, hollow, hour, inlet, instant, interim,
   interlude, intermezzo, intermission, intermittence, interregnum,
   interruption, interstice, juncture, kairos, lack, lacuna, lapse,
   laying open, layoff, leak, leap, less semitone, letup, level, lull,
   mark, meantime, meanwhile, measure, melodic interval, minute,
   missing link, moment, moment of truth, need, notch, note, nuance,
   octave, off-time, omission, opening, opening up, orifice, outage,
   outlet, parallel octaves, parenthesis, pas, passageway, pause, peg,
   period, pitch, plane, plateau, point, point of repose, pore,
   pregnant moment, proportion, psychological moment, quiet spell,
   range, ratio, reach, recess, relief, remission, remove, respite,
   rest, resting point, round, rung, scale, scope, season, second,
   semitone, seventh, shade, shadow, shortage, sixth, slot, space,
   span, spell, split, stage, stair, stand-down, standard, stay, step,
   stint, stoma, stretch, suspension, third, throwing open, time,
   time lag, time off, time out, tone, tread, truce, ullage,
   uncorking, unison interval, unstopping, vacation, void, wait, want,
   wantage, while, whole step, yawn



The Free On-line Dictionary of Computing (30 December 2018):

interval

    A set of real numbers bounded by two real
   numbers - the endpoints or bounds.  The set may or may not
   include either endpoint, leading to four possibilities:

    closed                   [a, b]  a <= x <= b
    open                     (a, b)  a < x < b
    left-open, right-closed  (a, b]  a < x <=b
    left-closed, right-open  [a, b)  a <= x < b

   See closed interval, open interval.

   (2015-04-26)


Bouvier's Law Dictionary, Revised 6th Ed (1856):

INTERVAL. A space of time between two periods. When a person is unable to
perform an act at any two given periods, but in the interval he has
performed such act, as when a man is found to be insane in the months of
January and March, and he enters into a contract or makes a will in the
interval, in February, he will be presumed to have been insane at that time;
and the onus will lie to show his sanity, on the person who affirms such
act. See Lucid interval.