I. ˌfull-ˈlength¹ adjective

1. full-length mirror/photograph/portrait etc a mirror etc that shows all of a person, from their head to their feet

2. full-length skirt/dress/coat etc a skirt etc that reaches the ground, or is the longest possible for that particular type of clothing:
a full-length evening dress

3. full-length play/book/film etc a play etc that is the normal length:
Stravinsky’s only full-length opera

[TahlilGaran] Dictionary of Contemporary English ▲

II. full-length² adverb
someone who is lying full-length is lying flat with their legs straight out:
Ali was stretched out full-length on the couch.

[TahlilGaran] Dictionary of Contemporary English ▲