on and off

adverb

: with periodic cessation : off and on, intermittently

Lucy was sick on and off for two years before doctors were able to discover what was wrong.

—Jo Abi

on-and-off

ˈȯn-ən(d)-ˈȯf 

adjective

It took more than 20 break-ups for Melissa Meagher to realise her six-year on-and-off relationship with her ex had to end for good.

—Sophie Aubrey

Word History

First Known Use

1668, in the meaning defined above