- fitful, spasmodic - occurring in spells and often abruptly; "fitful bursts of energy"; "spasmodic rifle fire"
Antonym: continual (indirect, via sporadic)
- fitful, interrupted, off-and-on - intermittently stopping and starting; "fitful (or interrupted) sleep"; "off-and-on static"
Antonym: unbroken (indirect, via broken)