I was suddenly worried that my use of "BF" would be interpreted as "Best Friend" instead of "Boy Friend". Happily I discovered that BF is listed as Boy Friend for the first three entries on the Urban Dictionary, which is like the OED only way less up itself. Interestingly, one commentator suggested that BF in caps is preferred for Best Friend, and bf, lower case, for boy friend. Hm. I'm not convinced, but it does save me from having to come up with a clever euphemism.