Antonyms of adj half-hourly

1 sense of half-hourly

Sense 1
half-hourly -- (occurring ever half hour)

INDIRECT (VIA periodic) -> aperiodic, nonperiodic -- (not recurring at regular intervals)

Similarity of adj half-hourly

1 sense of half-hourly

Sense 1
half-hourly -- (occurring ever half hour)
       => periodic (vs. aperiodic), periodical -- (happening or recurring at regular intervals; "the periodic appearance of the seventeen-year locust")

Synonyms of adv half-hourly

1 sense of half-hourly

Sense 1
half-hourly -- (every thirty minutes, every half hour)