expression, noun
striking while defending; countering an opponent's attack
Martial arts term: a timing concept where one strikes the opponent at the moment they initiate an attack, effectively countering while defending. Often contrasted with 先の先 (sen no sen) and 後の先 (go no sen).
対の先は、相手が打ってくる瞬間にこちらも打つ高度な技だ。
Tai no sen is an advanced technique where you strike at the very moment your opponent attacks.
From 対 (tai, 'opposing') + の (no, possessive particle) + 先 (sen, 'initiative' or 'before'), literally 'the initiative of opposing'. The exact historical derivation within martial arts is uncertain.