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]

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

interval

    A set (of numbers) bounded by two elements -
   the endpoints or bounds.  The interval may include or exclude
   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

   Intervals are typically defined on real numbers but may also
   be defined on integers or any other type that has an
   partial order.

   (2019-08-31)