つぼんだそうだ
窄んだそうだ
tsubonda sōda

Godan Verb (mu)
Evidential Auxiliary

Expresses hearsay about a past event ("I heard that...") of すぼむ

1. Narrowed, it seems.; It's said it narrowed.

Past/Perfective
Hearsay Evidence
Usually Written in Kana