Green’s Dictionary of Slang

1. irritable, irascible.

1848		Family Companion n.p.: I never did feel so streaky and mean before [DA].
1864, 1867, 1870		Hotten Sl. Dict.
1872		Schele De Vere Americanisms 637: Streaked or streaky, well known to English low life, are favorite words with Western men, to whom ‘to feel streaked,’ conveys the utmost apprehension of which they are capable.

2. (orig. baseball j., also stripy) variable in character, unstable, changeable .

1970		D. Jenkins Dogged Victims 110: [He] could not hide the conviction that almost all of the big-time players had about their putting. It was average. It was streaky.
1988		(ref. to late 19C) McGill Dict. of Kiwi Sl. 109/1: stripy streaky, unconvincing, variable; late C19.
2003		McGill Reed Dict. of N.Z. Sl. [as cit. 1988].
2024		D. Rucker Life’s Too Short 110: [of basketball] I’m streaky, but once I heat up, I become unconscious.