Straight flush? Smooth! (4)
I believe the answer is:
even
I believe this is a triple definition!
'straight' is the first definition.
(similar in meaning)
'flush?' is the second definition.
('even' can be similar in meaning to 'flush')
'smooth' is the third definition.
(I know that smooth can be written as even)
(Other definitions for even that I've seen before include "Not bumpy" , "Not odd; flat" , "Like half the numbers" , "Tied" , "Constant" .)