Meaning of “line” - Learner’s Dictionary

line

verb [ T ] uk us /laɪn/

to form a row along the side of something:

Trees and cafes lined the street.
be lined with sth

If a piece of clothing is lined with a material, its inside is covered with it:

a jacket lined with fur

(Definition of “line verb” from the Cambridge Learner’s Dictionary © Cambridge University Press)