groundless; entirely contrary to fact

the end of the month

completely deaf

being kept uninformed, being kept in the dark / the upper gallery where the dialogue is not heard well (of a theatre)

the first time one has heard of something; news to ...

realm, territory, occupied area / field (area of expertise) / (mathematics) domain

strike, a work stoppage / a student revolt, where students abandon their classes and examinations as a group

mood

river basin

(fandom slang) exposed skin of the thigh between the hem of a miniskirt and thigh-high socks