"imperative" in the noun sense
1. imperative mood, imperative, jussive mood, imperative form
a mood that expresses an intention to influence the listener's behavior
2. imperative
some duty that is essential and urgent
"imperative" in the adjective sense
1. imperative
requiring attention or action
"as nuclear weapons proliferate, preventing war becomes imperative"
"requests that grew more and more imperative"
2. imperative
relating to verbs in the imperative mood
Source: WordNet® (An amazing lexical database of English)
Princeton University "About WordNet®."
WordNet®. Princeton University. 2010.
View WordNet® License