Added 9 October 2026 thetis noun Categories: PeopleRare Words noun ! Definition from WordNet 3.1, Princeton University. More about thetis at Wordnik → Where our words come from → (Greek mythology) one of the 50 Nereids; mother of Achilles by Peleus. Related Words: nymphpasitheaianthetheianemertesargiopeachillescydippetisiphonechryseisthebethesiphone Back to today's word