See plump in Webster's New World Roget's A-Z Thesaurus II
verb
To drop or sink heavily and noisily:
flop, plop, plunk. See rise
phrasal verb plump forTo aid the cause of by approving or favoring:
advocate, back, champion, endorse, get behind, recommend, side with, stand behind, stand by, support, uphold. Idioms: align oneself with, go to bat for, take the part of. See support
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