Wiktionary
vb. 1 (context transitive English) To put a plug or bung into something to prevent leakage. 2 (context transitive English) To reinforce something weak
Usage examples of "plug up".
It was actually extremely unprofessional for that mechanic - Terry, I think he is - to push the substitute plug up into the sump, but Basil Rudd won't hear a word against him, and I suppose there was no harm done.
Dust comin' up an' spoilin' ever'thing so a man didn't get enough crop to plug up an ant's ass.
But if we plug up them loading-and-fuse holes, folks won't realize they're holler.
Hymie had to play chess with the waybills while I worked like a madman to plug up the gaps.
Perry all at once how many holes he will have to plug up, for he is bound to get frantic about it and make a fool of himself.
He felt like the captain of a sinking ship, running around vainly trying to plug up the holes.
Poor Lazarus there, chattering his teeth against the curbstone for his pillow, and shaking off his tatters with his shiverings, he might plug up both ears with rags, and put a corn-cob into his mouth, and yet that would not keep out the tempestuous Euroclydon.