Sporadic (12)
'sporadic' is the definition.
(associated in meaning)
This is all the clue.
(Another definition for infrequent that I've seen is " Rare".)
'sporadic' is the definition.
(similar in meaning)
This is the entire clue.
(Other definitions for intermittent that I've seen before include "Not continuous or steady" , "Occurring irregularly" , "Occasional" , "Spasmodic" , "Occurring at intervals" .)