(verb, transitive) have intercourse with unoffenive slang term. to have intercourse with This verb is used only transitively; it does not have the intransitive use that 'fuck' and 'screw' have: 'John diddled Mary.' '*John and Mary were diddling.'
DIDDLE
Meaning of DIDDLE in English
Slang English vocab. Английский сленговый словарь. 2012