infrequent

As an adverb rarely

is not occurring at a regular interval; seldom; not often.

As an adjective infrequent is

infrequent.

As adjectives the difference between infrequent and intermittent

is that infrequent is not frequent; not happening frequently while intermittent is stopping and starting at intervals; coming after a particular time span; not steady or constant.

As a noun intermittent is

an intermittent fever or disease.

As an adjective infrequent

is infrequent.

As a noun oligomenorrhoea is

(medicine) unusually infrequent menstruation.