infrequently
Word family (noun) frequency ≠ infrequency (adjective) frequent ≠ infrequent (verb) frequent (adverb) frequently ≠ infrequently
From Longman Dictionary of Contemporary Englishinfrequentlyin‧fre‧quent‧ly /ɪnˈfriːkwəntli/ adverb 1 not often SYN rarely OPP frequently Jeremy does play cricket, but very infrequently.2 → not infrequently