nidan verb (lower class) with 'ru' ending (archaic), intransitive verb
be wavy; be curled; be frizzled
Archaic intransitive verb meaning to be wavy, curled, or frizzled. In modern Japanese, this meaning is expressed by 縮れる (ちぢれる). The form 縮る is a classical lower bigrade (Nidan) verb.
See also: 縮れる
古典では「髪が縮る」のように用いられた。
In classical texts, it was used like 'hair becomes wavy/curled'.