Definition of gum up phrasal verb from the Oxford Advanced American Dictionary

 

gum up

 phrasal verb
phrasal verb
 
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Phrasal Verbs

gum somethingup

[usually passive](informal)
 
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to cover or fill something with a sticky substance so that it stops moving or working as it should Open and close the valves occasionally so they don't get gummed up.
See the Oxford Advanced Learner's Dictionary entry: gum up