Masturbation, in case subtlety's not your thing. Tommy tank. You know.
"Knit one purl one knit one purl- AND cast off..."
"No. I was knitting."
(Perjorative) : "You dirty little knitter !"
(Descriptive) *When a pretty girl (or boy- we must be inclusive here) walks into view* "Ah- a new pattern!"
(And if 'new pattern' has been particularly apposite:) "I blunted my piggin' needle last night. Dropped a stitch".
Jack: I went knitting with your mom and sister, Jill. It was pretty fun actually.
Jill: (unaware of the meaning of knitting) Alright then..