The Collaborative International Dictionary of English v.0.48:

Tide \Tide\, n. [AS. t[imac]d time; akin to OS. & OFries.
   t[imac]d, D. tijd, G. zeit, OHG. z[imac]t, Icel. t[imac]?,
   Sw. & Dan. tid, and probably to Skr. aditi unlimited,
   endless, where a- is a negative prefix. [root]58. Cf.
   Tidings, Tidy, Till, prep., Time.]
   1. Time; period; season. [Obsoles.] "This lusty summer's
      tide." --Chaucer.
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            And rest their weary limbs a tide.    --Spenser.
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            Which, at the appointed tide,
            Each one did make his bride.          --Spenser.
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            At the tide of Christ his birth.      --Fuller.
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   2. The alternate rising and falling of the waters of the
      ocean, and of bays, rivers, etc., connected therewith. The
      tide ebbs and flows twice in each lunar day, or the space
      of a little more than twenty-four hours. It is occasioned
      by the attraction of the sun and moon (the influence of
      the latter being three times that of the former), acting
      unequally on the waters in different parts of the earth,
      thus disturbing their equilibrium. A high tide upon one
      side of the earth is accompanied by a high tide upon the
      opposite side. Hence, when the sun and moon are in
      conjunction or opposition, as at new moon and full moon,
      their action is such as to produce a greater than the
      usual tide, called the spring tide, as represented in
      the cut. When the moon is in the first or third quarter,
      the sun's attraction in part counteracts the effect of the
      moon's attraction, thus producing under the moon a smaller
      tide than usual, called the neap tide.
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   Note: The flow or rising of the water is called flood tide,
         and the reflux, ebb tide.
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   3. A stream; current; flood; as, a tide of blood. "Let in the
      tide of knaves once more; my cook and I'll provide."
      --Shak.
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   4. Tendency or direction of causes, influences, or events;
      course; current.
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            There is a tide in the affairs of men,
            Which, taken at the flood, leads on to fortune.
                                                  --Shak.
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   5. Violent confluence. [Obs.] --Bacon.
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   6. (Mining) The period of twelve hours.
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   Atmospheric tides, tidal movements of the atmosphere
      similar to those of the ocean, and produced in the same
      manner by the attractive forces of the sun and moon.

   Inferior tide. See under Inferior, a.

   To work double tides. See under Work, v. t.

   Tide day, the interval between the occurrences of two
      consecutive maxima of the resultant wave at the same
      place. Its length varies as the components of sun and moon
      waves approach to, or recede from, one another. A
      retardation from this cause is called the lagging of the
      tide, while the acceleration of the recurrence of high
      water is termed the priming of the tide. See Lag of the
      tide, under 2d Lag.

   Tide dial, a dial to exhibit the state of the tides at any
      time.

   Tide gate.
      (a) An opening through which water may flow freely when
          the tide sets in one direction, but which closes
          automatically and prevents the water from flowing in
          the other direction.
      (b) (Naut.) A place where the tide runs with great
          velocity, as through a gate.

   Tide gauge, a gauge for showing the height of the tide;
      especially, a contrivance for registering the state of the
      tide continuously at every instant of time. --Brande & C.

   Tide lock, a lock situated between an inclosed basin, or a
      canal, and the tide water of a harbor or river, when they
      are on different levels, so that craft can pass either way
      at all times of the tide; -- called also guard lock.

   Tide mill. (a) A mill operated by the tidal currents.
      (b) A mill for clearing lands from tide water.

   Tide rip, a body of water made rough by the conflict of
      opposing tides or currents.

   Tide table, a table giving the time of the rise and fall of
      the tide at any place.

   Tide water, water affected by the flow of the tide; hence,
      broadly, the seaboard.

   Tide wave, or Tidal wave, the swell of water as the tide
      moves. That of the ocean is called primitive; that of bays
      or channels derivative. See also tidal wave in the
      vocabulary. --Whewell.

   Tide wheel, a water wheel so constructed as to be moved by
      the ebb or flow of the tide.
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WordNet (r) 3.0 (2006):

tide rip
    n 1: a stretch of turbulent water in a river or the sea caused
         by one current flowing into or across another current [syn:
         rip, riptide, tide rip, crosscurrent,
         countercurrent]