Porn industry usually uses it to mean a cumbath, more than one guy coming on a woman, usually her face but sometimes her whole body.

type it into Google(TM) ... you shan't be disappointed!  

except, the accepted spelling is:  Bukkake  (the 2 k's come first)

can you at all tell that i changed your spelling of it in the Subject line of this message?  ... that's why it's so often mispelled and still goes unnoticed

happy splashing!