noun
meeting of Vega and Altair; Tanabata star meeting
Poetic term for the annual meeting of the stars Vega (Orihime) and Altair (Hikoboshi) on the night of Tanabata (July 7th). Often used in classical poetry and romantic contexts.
See also: 七夕
七夕の夜、星合を願って短冊を書く。
On the night of Tanabata, we write wishes on strips of paper, hoping for the meeting of the stars.
この和歌は星合を詠んだものだ。
This waka poem is about the meeting of the love stars.
七夕 is the common word for the Tanabata festival itself, while 星合 specifically refers to the celestial meeting of the two stars, often with a poetic or romantic nuance.
Compound of 星 (hoshi, 'star') and 合い (ai, 'meeting'). The reading ほしあい is a straightforward combination. The term is deeply associated with the Tanabata legend.