Something that musicians, especially percussionists, do. Splitting triplets involves playing eighth notes and triplets at the same time, whether by combination of tapping one's foot, hacking, drumspeak, or a musical instrument, or whatever. In drumspeak a split triplet is "blut diga dut", with the blut being the first note of both the triplet and eighth note; the di- being the second note of the triplet, the -ga being the second eighth note, and the last dut being the third note of the triplet. Try hacking on your legs, with your dominant hand doing the triplets and your off-hand doing the eighth notes.