Green’s Dictionary of Slang

knock back v.

1. to cost, e.g. that’ll knock you back a bit.

[UK]Partridge DSUE (8th edn) 654: C.20.
[UK]Guardian 15 July [Internet] How much do the top ones knock you back? Between £300 and £370.

2. to fine someone.

[UK]Partridge DSUE (8th edn) 654: since ca. 1910.

3. (also bang back, knock about) to eat, to drink, esp. to finish off one’s drink.

[UK]‘Leslie Charteris’ Enter the Saint 157: Simon knocked back a couple of pints of beer.
[UK]J. Curtis Gilt Kid 122: Been knocking it about a bit this afternoon.
[UK]S. Jackson Indiscreet Guide to Soho 116: He knocked back his whisky and ordered another.
[US]R. Chandler Long Good-Bye 54: He opened the drawer and put a bottle and a shot glass on the desk. He poured it full to the brim and knocked it back in one lump.
[UK]H.E. Bates When the Green Woods Laugh (1985) 284: Pop [...] ordered himself a double Johnny Walker and urged Angela and the Brigadier to knock theirs back and quick.
[UK](con. 1961) J. Rosenthal Spend, Spend, Spend Scene 1: I’m not surprised. Rate you’ve been knocking them back.
[UK]F. Taylor Auf Wiedersehen Pet Two 23: Den’s knocking back the hard stuff, isn’t he?
[Aus]C. Bowles G’DAY 88: SHANE. I musta knocked back a few. AARON. Ya were paraletic.
[Ire]P. Howard The Joy (2015) [ebook] [A] bunch of altar boys who were knocking it back in the vestry and were pissed at Mass.
[UK]D. Farson Never a Normal Man 33: The guests knocked back their cocktails.
[UK]N. Griffiths Grits 47: A bang back what’s left uv thuh Guinnness.
[US]D. Henry Sterry Chicken (2003) 47: She [...] knocked back a few snorts.
[Aus]L. Redhead Thrill City [ebook] None of the subcultures minded a drink [...] Everyone was knocking back beer, wine and premixed rum and coke with gusto.

4. (orig. Aus./N.Z.) to reject [knockback n. (1)].

[Aus]L. Glassop We Were the Rats 104: Ya still goin’ ter be true to Margaret? Still goin’ to keep knockin’ back the sheilas?
[Aus]D. Niland Shiralee 29: Don’t offer me money [...] I mightn’t knock it back.
[Aus]S. Gore Holy Smoke 63: If the foreman builder was to knock back a bit of crook stone.
[Aus] in K. Gilbert Living Black 100: I’m glad those boys knocked those jobs back.
[Aus]N. Keesing Lily on the Dustbin 137: When a young Australian man ‘puts the hard word on’ a girl who does not welcome his sexual importunities she will ‘knock him back’ (tell him to ‘go jump in the lake’ or ‘take a long walk off a short pier’ — or worse).
[UK]I. Welsh ‘A Smart Cunt’ in Acid House 201: Knocked back by his girlfriend.
[Ire]P. Howard The Joy (2015) [ebook] [H]e put in for early release, built up his hopes and then got knocked back.
[Aus]R.G. Barrett Goodoo Goodoo 26: Les didn’t think it would be doing the right thing accepting money from a grieving mother and was about to knock it back.
[UK]N. Griffiths Grits 253: Ee tried it on with me at a party last week but a knocked im back.