"periodic" in the adjective sense
1. periodic, periodical
happening or recurring at regular intervals
"the periodic appearance of the seventeen-year locust"
2. periodic, occasional
recurring or reappearing from time to time
"periodic feelings of anxiety"
Source: WordNet® (An amazing lexical database of English)
Princeton University "About WordNet®."
WordNet®. Princeton University. 2010.
View WordNet® License