Undershirt (noun)

1. A shirt worn next to the skin and under other clothes.
2. A shirt worn to provide warmth and absorb perspiration.

Origin:

Early 20th century: from under- + shirt.

Examples:

1. He wore an undershirt under his dress shirt.
2. She chose a white undershirt to wear with her suit.
3. He preferred to wear a tank top as an undershirt.
4. The undershirt was designed to be worn discreetly.
5. The undershirt was an important part of a man's wardrobe.