frequent B1

/ˈfriːkwənt/ Happening or doing something often.

infrequent C2+

/ɪnˈfrikwənt/ not occurring often; rare

infrequently C2+

/ɪnˈfrikwəntli/ not often; rarely

infrequency C2+

/ɪnˈfrikwənsi/ the state of happening rarely or seldom

unfrequented C2+

/ˌʌnfriˈkwɛntɪd/ rarely visited; secluded