I. ˈ ̷ ̷ˌ ̷ ̷, ˌ ̷ ̷ˈ ̷ ̷ noun
Usage: often attributive
Etymology: thumb (I) + nail
1. : the nail of the thumb
2. : something small, brief, or concise
a thumbnail sketch
II. ˈ ̷ ̷ˌ ̷ ̷ transitive verb
: to make a thumbnail sketch of
the minor characters have been methodically thumbnailed in conventional types — J.S.Shrike
practically everybody anybody ever heard of is cited, thumbnailed, keelhauled, cuddled — Time