不

impenetrability

unavailable choice

pitcher's misjudgment (misjudgement)

unfair competition

nonfarming land; untilled land

veto; rejection

emergency landing; forced landing; crash landing

poor preparation; poor arrangements

nonconformist; free-thinker

irregular forces; guerrillas

negative reaction; unsuccessful vaccination

needy circumstances

deficit; shortage

Mathematics

indefinite metric space

Grammar

infinitive mood

dishonored check; dishonoured cheque

ice-free sea

antifreeze

nonassimilation

nonconductibility

nonrecognition

papal infallibility

indivisibility

Law

unwritten law; common law