The Collaborative International Dictionary of English v.0.48:

Ebb \Ebb\, v. i. [imp. & p. p. Ebbed; p. pr. & vb. n.
   Ebbing.] [AS. ebbian; akin to D. & G. ebben, Dan. ebbe. See
   2d Ebb.]
   1. To flow back; to return, as the water of a tide toward the
      ocean; -- opposed to flow.
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            That Power who bids the ocean ebb and flow. --Pope.
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   2. To return or fall back from a better to a worse state; to
      decline; to decay; to recede.
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            The hours of life ebb fast.           --Blackmore.

   Syn: To recede; retire; withdraw; decay; decrease; wane;
        sink; lower.
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The Collaborative International Dictionary of English v.0.48:

Ebb \Ebb\ ([e^]b), n. (Zo["o]l.)
   The European bunting.
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The Collaborative International Dictionary of English v.0.48:

Ebb \Ebb\, n. [AS. ebba; akin to Fries. ebba, D. eb, ebbe, Dan.
   & G. ebbe, Sw. ebb, cf. Goth. ibuks backward; prob. akin to
   E. even.]
   1. The reflux or flowing back of the tide; the return of the
      tidal wave toward the sea; -- opposed to flood; as, the
      boats will go out on the ebb.
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            Thou shoreless flood which in thy ebb and flow
            Claspest the limits of morality!      --Shelley.
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   2. The state or time of passing away; a falling from a better
      to a worse state; low state or condition; decline; decay.
      "Our ebb of life." --Roscommon.
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            Painting was then at its lowest ebb.  --Dryden.
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   Ebb and flow, the alternate ebb and flood of the tide;
      often used figuratively.
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            This alternation between unhealthy activity and
            depression, this ebb and flow of the industrial.
                                                  --A. T.
                                                  Hadley.
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The Collaborative International Dictionary of English v.0.48:

Ebb \Ebb\, v. t.
   To cause to flow back. [Obs.] --Ford.
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The Collaborative International Dictionary of English v.0.48:

Ebb \Ebb\, a.
   Receding; going out; falling; shallow; low.
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         The water there is otherwise very low and ebb.
                                                  --Holland.
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WordNet (r) 3.0 (2006):

ebb
    n 1: a gradual decline (in size or strength or power or number)
         [syn: ebb, ebbing, wane]
    2: the outward flow of the tide [syn: ebb, reflux]
    v 1: flow back or recede; "the tides ebbed at noon" [syn: ebb,
         ebb away, ebb down, ebb out, ebb off] [ant:
         surge, tide]
    2: hem in fish with stakes and nets so as to prevent them from
       going back into the sea with the ebb
    3: fall away or decline; "The patient's strength ebbed away"