“Students avoid boring professors” is ambiguity?

Solution 1:

The ambiguity comes from the word "boring," which can be interpreted as an adjective or a noun (see gerund).

You read the sentence as:

Students avoid professors who are boring.

(Which I think is the most natural interpretation, unless there is further context.) Here "boring" is an adjective, modifying "professors."

However, it can also be interpreted as:

Students avoid making their professors bored.

Here "boring" is a noun, referring to the act of making someone feel bored.

Solution 2:

The two possible meanings:

1. Students stay away from boring professors.
2. Students try hard not to bore their professors.

But I believe everyone else has told you the same. :-)

Solution 3:

If boring is taken as an adjective, it means "Students stay away from professors who are boring." But boring can also be taken as the gerund form of the verb to bore, in which case the sentence would mean "Students do not bore professors."