(countable, uncountable) Anything that forms, defines, or marks the edge of something.
The decorative edging around the door makes it easier to find in the dark.
A means was found, for example, of fitting rubber edging to the doors and still retaining the handle and door lock. 1951 March, “Reconstruction of London Transport Rolling Stock”, in Railway Magazine, page 160:
(countable, uncountable) A technique involving the placement of the edge of the climbing shoe on a sharp hold.
(countable, uncountable) The operation of shaping or dressing the edge of anything, as of a piece of metal.
(countable, uncountable) The sexual technique of maintaining a high level of sexual arousal for an extended period of time without reaching orgasm.