Sports bra
From Tardis Wiki, the free Doctor Who reference
Sports bras were a form of bra, worn as sportswear. They were designed similar to a halter top; allowing women to wear them publicly when working out. The design was meant to secure breasts and prevent movement due to physical activity, rather than comfort.
Some women chose to wear sports bras over wearing normal ones. Sallh Morgan kept several sports bras in her room onboard the Black TARDIS, the fact of which she used as proof that the room did not belong to Hex. (AUDIO: Black and White)