Green’s Dictionary of Slang

bar n.3

[SE bar of music]

(UK/US black) a rap lyric.

[UK]Skepta ‘Lyrics’ 🎵 Lord of the Mics, you was spitting that heat / But right now, your bars ain't on fleek.
Jeezy ‘Never Settle’ 🎵 I'ma leave the bars to Kendrick and Cole I speak that real life.
[UK]G. Krauze What They Was 30: It was a wrap after that [...] I couldn’t even spit the rest of my bars.