To chew, especially of a toothless person or animal.
To deepen and enlarge the spaces between the teeth of (a worn saw), as with a gummer.
(sometimes with up) to apply an adhesive or gum to; to make sticky by applying a sticky substance to.
To stiffen with glue or gum.
(sometimes with together) to inelegantly attach into a sequence.
(with up) to impair the functioning of a thing or process.
Example: "That cheap oil will gum up the engine valves."