at some indefinite or indeterminate point of time

He will arrive sometime next week.

at an indefinite future time

Come to see me sometime.

Archaic . sometimes; on some occasions.

Archaic . at one time; formerly.

having been formerly; former

The diplomat was a sometime professor of history at Oxford.

being so only at times or to some extent

Traveling so much, he could never be more than a sometime husband.

that cannot be depended upon regarding affections or loyalties

He was well rid of his sometime girlfriend.

adjective

erstwhile , former , old , once , onetime , past , previous , quondam , whilom , formerly , intermittently , occasional , periodically

adverb

former , formerly , late , once , previous , quondam , someday