noun
training clothes; practice suit
Specifically refers to the uniform worn during practice in martial arts such as judo, kendo, aikido, etc. Not used for general sportswear.
柔道の稽古着を洗濯した。
I washed my judo practice uniform.
新しい稽古着を買うためにスポーツ店に行った。
I went to a sports shop to buy a new training suit.
Compound of 稽古 (keiko, 'practice, training') and 着 (gi, 'clothing, wear'). The reading けいこぎ is a straightforward combination of the on'yomi of 稽古 and the kun'yomi of 着.