Noun
a finger used in pulling the trigger of a firearm
the forefinger
(medicine) difficulty encountered in finger flexion or extension caused by the narrowing of the sheath that surrounds that finger's tendon
Source: en.wiktionary.orgNobody could have predicted that two of them, Dylan Ellis, 26, and Oliver Martin, 25, would soon be dead — gunned down in the wee hours of Friday the 13th, June 2008, by a stone cold killer with an itchy trigger finger who has nev. Source: Internet
"They told me I couldn't be in the Army without a trigger finger," Miller recollected in a recent interview. Source: Internet