speedo

noun1

1. •
   (informal) A speedometer, particularly one in a race car or other automobile.

   • The main instruments are in the centre of the dash, finished in silver (grey on the GP); consisting of a circular speedo with petrol and temperature gauges on either side. — 2012

noun2

1. •
   A tight-fitting swimsuit, especially commonly worn by competitive swimmers and divers. Usually implies a brief or bikini style swimsuit.

   • I could tell that she was a serious swimmer, because every time I saw her at the pool she was wearing a Speedo of one design or another.
2. •
   (by restriction) A male swimsuit, very tight fitting and small, brief-style, and not a thong-type.

   • She called down from upstairs, "He'll be out in a minute: he's just putting his Speedo on."