can't nail (something) down

can't nail (something) down

Unable to complete, do correctly, or be certain of some task or thing. I've been working on my speech for an hour, but I can't seem to nail it down. They couldn't nail down the terms of their agreement. I know I've heard this song before, but I can't quite nail it down.
See also: down, nail
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
See also:
Idioms browser ?
Full browser ?