Bubble picking refers to a single-note guitar line often heard in R&B and funk guitar.
Though not chordal, the bubble line serves rhythmic purposes.
Bubble lines are often syncopated and derived from 16th-note subdivisions.
Bubble picking often features a muted staccato sound via left- and right-hand muting.
Bubble picking examples
Pioneering funk guitarists (like David Williams) who worked with Michael Jackson often used bubble picking. P.Y.T. is a prime example along with the outro of Don't Stop Til You Get Enough.
Modern funksters Vulfpeck collab'd with Cory Wong on this tune that prominently features bubble picking. Check out Cory's part in the intro for some stellar bubble lines.