A pair of shorts or briefs worn for swimming or bathing.(noun)
Wiktionary.org : Text is available under the Creative Commons Attribution-ShareAlike License
Use "bathing trunks" in a sentence
"He had a terrible time explaining, and a worse time when I got it straight, that what Worldic wanted were some pictures of me reclining in bathing trunks under a sun umbrella beside a bosomy model in a bikini."