Answer:
So-called "troublesome" verbs are those that are frequently misused. In particular, there are some pairs of verbs that sound similar, but have different meanings. The three classic examples are "sit" and "set", "lie" and "lay" and "rise" and "raise".
Another "troublesome" verb pair for some people is "borrow" and "lend"--which have opposite meanings! These are further confused by the extremely common misuse of the noun "loan" in place of the verb "lend".