cock·le·shell 
(kŏkəl-shĕl′)
(kŏkəl-shĕl′)n.
1.
a. The shell of a cockle.
b. A shell similar to that of a cockle.
2. Nautical A small light boat.
- unfoldment
- unforeseen
- unforgettability
- unforgettable
- unforgettableness
- unforgettably
- unforgivable
- unforgiving
- unformatted
- unformed
- unfortunate
- unfortunately
- unfounded
- unfoundedly
- unfoundedness
- unfreeze
- unfrequented
- unfriend
- unfriended
- unfriendliness
- unfriendly
- unfrock
- unfruitful
- unfruitfully
- unfruitfulness