A poetic or literary term for the feeling of lovesickness, often evoking a classical or romantic tone. Not an everyday clinical term.
彼は恋草に悩まされて、食事も喉を通らなかった。
He was so afflicted with lovesickness that he couldn't even eat.
万葉集には恋草を詠んだ歌が多く見られる。
Many poems in the Man'yōshū sing of lovesickness.
Compound of 恋 (koi, 'love') and 草 (kusa, 'grass' or 'herb'), literally 'love grass'. The exact origin is uncertain; it may derive from classical poetic metaphor where love is likened to a plant that grows or causes suffering.