godan verb (-ru), intransitive verb
get thin; become slender; taper off
Describes something becoming physically thinner or narrower, or a quantity/condition diminishing gradually. Often used for body parts, objects, or abstract things like income.
病気で足が細ってしまった。
My legs have gotten thin from illness.
この道は先のほうで細っている。
This road tapers off ahead.