| on rare occasions(expression, idiom, adverb, barely, terrifically) |
| once in blue moon(expression, idiom, adverb, barely, terrifically) |
| orbital(adjective, intermittent, isochronal, seasonal) |
| periodic(adjective, irregular, infrequent, sporadic, intermittent) |
| periodical(adjective, irregular, infrequent, sporadic, intermittent) |
| rarely(adverb, exceptionally, terrifically, unfrequently) |
| recurrent(adjective, irregular, infrequent, sporadic, intermittent) |
| remarkably(adverb, barely, terrifically, seldom, unfrequently) |
| scarcely ever(expression, adverb, barely, terrifically, seldom) |
| seasonal(adjective, irregular, infrequent, sporadic, intermittent) |
| so |
| so much(expression, terrifically, unfrequently) |
| stop-and-go(adjective, irregular, infrequent, sporadic, intermittent) |
| surprisingly(terrifically, unfrequently) |
| terrifically |
| uncertainly(adverb, intermittent, on-and-off) |
| uncommon(adverb, barely, terrifically, seldom, unfrequently) |
| unfrequently(adverb, barely, terrifically, seldom) |
| unoften(adverb, barely, terrifically, seldom, unfrequently) |
| unusually(adverb, barely, terrifically, seldom, unfrequently) |