connect

   1. to copulate

   The imagery is from joining or fastening together:

    ... two beautifully engraved figures of man and woman who were connecting at every tick of the clock. (F. Richards, 1936)

   Connection in this sense normally means extramarital copulation, although usually in the singular:

    Privates in the Blues... often formed very reprehensible connections with women of property, tradesmen's wives, and even ladies. (Mayhew, 1862 — 'the Blues' is a British regiment)

   and sometimes bestiality:

    ... others were homosexual, others who sought connection with animals (an illdocumented area in sexology). (Pearsall, 1969)

   2. a source of illegal narcotics

   The connection, in the jargon of drug usage, runs from the manufacturer to the retailer:

    [She] had got too much in the bank to be shagging every creep with a connect because she's too scared to go out and cop on her own. (Turow, 1999)