godan verb (-mu), intransitive verb
Primarily used for flowers closing their petals; also for other things that fold or shut in a similar way.
夕方になると、朝顔の花がつぼむ。
In the evening, morning glory flowers close.
チューリップは夜になるとつぼむ。
Tulips close at night.
godan verb (-mu), intransitive verb
get narrower; taper
Describes something becoming narrower toward one end, like a tube or a path. Related to すぼまる and すぼめる.
See also: 窄める (すぼめる) · 窄まる (すぼまる)
この道は奥に行くほどつぼんでいる。
This path gets narrower the further you go.
パイプの先がつぼんでいる。
The end of the pipe is tapered.