Although "trundle" sometimes means "to roll" or "to twirl," today the most common meaning is to move or travel in a clumsy, heavy way.
Part of speech:
usually the intransitive kind
("it trundles," "he trundled along," "that keeps trundling off")
but sometimes the transitive kind
("she trundled the wheelbarrow," "they trundled us off into the dark night").
Other forms: trundled, trundling, trundler(s)
How to use it:
Often we talk literally about tanks, buses, trucks, and other bulky vehicles that trundle through cities, trundle across highways, trundle along, trundle away, trundle in, etc.
If you talk about people or animals that trundle, you're saying that they're large and/or awkward in some way; for example, cows and oxen trundle, but songbirds don't. And you're often suggesting that they lack ferocity; for example, friendly cartoon dragons like Puff and Elliott trundle, but frightening CGI dragons like Smaug probably don't.
Now for the good part, where we get figurative! If you can imagine something moving at a sluggish, awkward pace, you can say that it trundles, that it trundles away, that it trundles off into obscurity, etc. So you might talk about fads, ideas, plans, dreams, programs, projects, periods of time and so on that trundle.
Treebeard trundles the hobbits off, their pudgy feet balanced on his branches.