JARK
Etymology 1
Noun
jark (plural jarks)
A seal (stamp or impression of a stamp).
Verb
jark (third-person singular simple present jarks, present participle jarking, simple past and past participle jarked)
(slang, military, British) To modify (weaponry) to disadvantage; especially, to attach and use a tracking device to covertly monitor its location.
Usage notes
(track weaponry): Both word and practice became common during the Ulster Troubles (1968-1998).
Etymology 2
Verb
jark (third-person singular simple present jarks, present participle jarking, simple past and past participle jarked)
Eye dialect spelling of jerk.
Source: Wiktionary