noun
railway frog
Technical term in railway engineering for the crossing point of two rails where the flanges of train wheels pass through.
轍叉の摩耗を定期的に点検する必要がある。
It is necessary to regularly inspect the wear of the railway frog.
The reading てっさ is a compound of 轍 (てつ, 'rut, wheel track') and 叉 (さ, 'fork, crossing'), describing the forked shape where rails cross. The exact historical derivation is uncertain.