General: tank top
A tank top (known as a vest in UK or a singlet in Australia/New Zealand) is a shirt manufactured without sleeves, or one where the sleeves have been cut off. Sleeveless shirts are worn by either gender, depending on the style. Tank tops are often worn by athletes in sports such as track and field and bicycling. Tank tops have been popular warm-weather casual wear in the United States since the 1970s, and are regarded as acceptable public casual dress in most warm weather locales. They are mostly preferred in hot climates, since the arm holes provide ventilation and the thin fabric provides comfort.
For "tank top" in British English, see sweater vest.
See also https://en.wikipedia.org/wiki/Vest