sporadic

adjectives

recurring in scattered and irregular or unpredictable instances
"a city subjected to sporadic bombing raids"
sporadic
antonym
continual
is similar to
occurring in spells and often abruptly
"fitful bursts of energy"; "spasmodic rifle fire"
fitful, spasmodic
is similar to
stopping and starting at irregular intervals
"intermittent rain showers"
intermittent
is similar to
recurring or reappearing from time to time
"periodic feelings of anxiety"
occasional, periodic
is similar to
not occurring at expected times
irregular, unpredictable
is similar to
not close together in time
"isolated instances of rebellion"; "a few stray crumbs"
isolated, stray
see also
not continuing without interruption in time or space
"discontinuous applause"; "the landscape was a discontinuous mosaic of fields and forest areas"; "he received a somewhat haphazard and discontinuous schooling"
discontinuous, noncontinuous
see also
not frequent; not occurring regularly or at short intervals
"infrequent outbursts of temper"
infrequent