noun
last line of a poem
Specifically the final line of a traditional poem, such as a tanka or haiku.
この短歌の結句は特に印象的だ。
The last line of this tanka is especially striking.
adverb
finally; in the end; after all
Adverbial use indicating that something happens as a final outcome, often after a process or expectation. Somewhat literary or formal.
長い議論の末、結句彼の提案が採用された。
After a long discussion, his proposal was finally adopted.
From 結 (けつ, 'conclude') + 句 (く, 'phrase/line'). The adverbial sense developed from the idea of reaching the final line or conclusion.