Green’s Dictionary of Slang

1. drunk.

1943		‘Myles na gCopaleen’ Faustus Kelly in ‘Flann O’Brien’ Stories & Plays (1973) 184: Yerrah, sure the man is only jarred.
1956		B. Behan Quare Fellow (1960) Act I: It’s my opinion that old Healey does be half-jarred a deal of the time.
1966		(con. 1954) J. McGrath Events While Guarding the Bofors Gun I iii: I’ve been on the bevvy, but I’m not jarred.
1970		C. Brown Down All the Days 5: I’m not jarred, Pop [...] just a few jars, that’s all – but not jarred.
1998		J. O’Connor Salesman 365: Loads of drink. Great crack. I suppose I’m a bit jarred.

2. used fig., in a mess.

1930

G. Milburn ‘Everywhere You Go’ in Hobo’s Hornbook 95: On the fritz in Kansas City, / Out in Denver things are jarred.