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2.
1. The act of sleazily coming on to a member of the opposite sex, often utilising alcohol, ridiculously colourful clothing and eye-watering lines of Austin Powers style calibre, usually delivered in an drawling accent straight-outta Surrey. A Schweffe can be of either sex.
Chap 1: Mate, did you see Georgie schweffing up Charles and the hunt ball last night? He could barely stand straight.

Chap 2: Ya, I tried to get close to ask if he was alright but she kicked me straight in the cock and told me to fuck off.
by Ballchops May 16, 2012
 
1.
The male or female form of interaction, with the opposite sex, including flirting or attempting to pull.

Or more loosely defined as any interaction/banter/chilling/pulling between any guy or girl.
Jem: Mate are you schweffing tonight?
Harry: Yeah thinking of schweffing the floor 8 girls actually, fancy schweffing along?
Jem: Yeah I was gonna see if Steve was up for a schweff, but apparently he's schweffing Ellie!
Harry: OK.. Schweff ya later!
by schweffatron3000 February 23, 2011