From WordNet (r) 2.0 (August 2003) [wn]:
tidal
adj : of or relating to or caused by tides; "tidal wave"
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Tidal \Tid"al\, a.
Of or pertaining to tides; caused by tides; having tides;
periodically rising and falling, or following and ebbing; as,
tidal waters.
[1913 Webster]
The tidal wave of deeper souls
Into our inmost being rolls,
And lifts us unawares
Out of all meaner cares. --Longfellow.
[1913 Webster]
Tidal air (Physiol.), the air which passes in and out of
the lungs in ordinary breathing. It varies from twenty to
thirty cubic inches.
Tidal basin, a dock that is filled at the rising of the
tide.
Tidal wave.
(a) See Tide wave, under Tide. Cf. 4th Bore.
(b) A vast, swift wave caused by an earthquake or some
extraordinary combination of natural causes. It rises far
above high-water mark and is often very destructive upon
low-lying coasts.
[1913 Webster]