noun
next word; what to say next
Almost always appears in the negative idiom 二の句が継げない, meaning 'to be at a loss for words' or 'to be unable to say anything further'. The noun itself is rarely used outside this phrase.
See also: 二の句が継げない
あまりの驚きに二の句が継げなかった。
I was so surprised that I couldn't say another word.
彼の突然の告白に、私は二の句が継げなかった。
At his sudden confession, I was at a loss for words.