The Collaborative International Dictionary of English v.0.48:
Flush \Flush\, a.
1. Full of vigor; fresh; glowing; bright.
With all his crimes broad blown, as flush as May.
2. Affluent; abounding; well furnished or suppled; hence,
Lord Strut was not very flush in ready. --Arbuthnot.
3. (Arch. & Mech.) Unbroken or even in surface; on a level
with the adjacent surface; forming a continuous surface;
as, a flush panel; a flush joint.
4. (Card Playing) Consisting of cards of one suit.
(a) A screw bolt whose head is countersunk, so as to be
flush with a surface.
(b) A sliding bolt let into the face or edge of a door, so
as to be flush therewith.
Flush deck. (Naut.) See under Deck, n., 1.
Flush tank, a water tank which can be emptied rapidly for
flushing drainpipes, etc.