Green’s Dictionary of Slang

1. anything obvious.

1984		Partridge DSUE (8th edn) 325/1: since ca. 1920.
1986		C. Bowles G’DAY 70: E’s flogged it. Sticks out like dog's balls.

2. anything excellent, admirable, first-rate.

1981		SuperBike Sept. n.p.: The Absolute Bollocks.
1989		C. Donald et al. [title] Viz: the dog’s bollocks: the best of issues 26 to 31.
1998		Guardian Sat. Rev. 5 Sept. 3: [The film] might be one of Tarantino’s strays, but it is the dog’s bollocks.
2004		N. ‘Razor’ Smith A Few Kind Words and a Loaded Gun 73: I thought the young Elvis was the dog’s bollocks.
2013		T. Black Ringer [ebook] n.p.: You weren't the dog's bollocks you thought you were.

3. a complete mess.

1996

P. Howard The Joy (2015) [ebook] He’s just not good enough. He’d chance his arm right enough – or rather mine – but he’d make a complete dog’s bollix of it [i.e. a complex tattoo].

4. a derisive retort.

1999

P. McCabe Mondo Desperado 27: ‘Thomas Aquinas! The two ends of a dog’s bollocks!’ and ‘I’ll give you informed conscience, you gimpy-looking hoor and that fucker along with you! You hear me?’.