PERIOD'IC PERIOD'ICAL, adjective 1. Performed in a circuit, or in a regular revolution in a certain time, or in a series of successive circuits; as the periodical motion of the planets round the sun; the periodical motion of the moon round the earth. 2. Happening by revolution, at a stated time; as, the conjunction of the sun and moon is periodical. 3. Happening or returning regularly in a certain period of time. The Olympiads among the Greeks were periodical, as was the jubilee of the Jews. 4. Performing some action at a stated time; as the periodical fountains in Switzerland, which issue only at a particular hour of the day. 5. Pertaining to a period; constituting a complete sentence. 6. Pertaining to a revolution or regular circuit.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI