folding fin

folding fin

[′fōld·iŋ ′fin]
(aerospace engineering)
A fin hinged at its base to lie flat, especially a fin on a rocket that lies flat until the rocket is in flight.
References in periodicals archive ?
5-kg rocket, designated 9M22U or M-21 OF, is spun first by a groove in the launch-tube and then by folding fins.