Green’s Dictionary of Slang

meet v.

SE in slang uses

In phrases

meet with mother thumb and her four daughters (v.)

to masturbate.

[US]B. Rodgers Queens’ Vernacular 116: mother and [her] four children (kwn NYC, black gay sl, late ’60s) the masturbator’s best girl friend – his hand: the thumb is the mother to the four fingers.
Sex-Lexis 🌐.
‘Dave and Julia’ at asstr.org 🌐 Dave was growing more frustrated. Dates with ‘Ma Thumb and her four daughters’ had given way to browsing the internet.