Wiktionary
vb. 1 (context intransitive English) To put on warm clothes. 2 (context transitive English) To put into a bundle.
WordNet
Usage examples of "bundle up".
Jamie undid it with a quick yank, wrapped the apron round my hand, and held the whole clumsy bundle up over my head.
You bundle up in your warm cloak, creep out of your cozy cottage, and draw your hood up over your face so only God will know you took pity on the village whore.
We watched the men bundle up their parachutes and move off through the dense undergrowth, chopping at it with jungle machetes.
Eventually, Enoch Root wraps the bundle up again, just like it was before.
But Buvrai, instead of paying heed when his brother, who had evidently taken leave of his senses, appeared to be ready to throw some kind of awkward bundle up to him, just turned away from the window at the crucial moment, expressing his disgust.