1 nail /ˈneɪl/ noun
plural nails
1 nail
plural nails
Learner's definition of NAIL
: a long, thin piece of metal that is sharp at one end and flat at the other end and that is used chiefly to attach things to wood see picture at carpentry; compare 1screw 1
: the hard covering at the end of a finger or toe : a fingernail or toenail
see also hangnail

a nail in the/someone's coffin

: something that makes it more likely that someone or something will fail, be destroyed, etc.

(as) hard/tough as nails

of a person
: very tough

hit the nail on the head

see 1hit

tooth and nail

see tooth
2 nail /ˈneɪl/ verb
nails; nailed; nailing
2 nail
nails; nailed; nailing
Learner's definition of NAIL
[+ object]
always followed by an adverb, adjective, or preposition : to attach (something) with a nail
: to catch (someone) doing something illegal or wrong
: to arrest or punish (someone) for doing something that is illegal or wrong
informal : to hit (someone or something) forcefully
US, informal : to make or do (something) in a perfect or impressive way

nail down

[phrasal verb]
nail (something) down or nail down (something)
: to make (something, such as a victory) certain to happen
: to find out or identify (something) exactly
: to make (something) definite or final