Here's an interesting grammar question that I don't know the answer to. A friend raised it in another forum and I'd like to get opinions on it.

A ohrasal verb consists of a main verb plus an adverb or preposition and has a non-obvious meaning. So "take on" has a meaning that isn't readily apparent from its constituent parts.

Now, my friend wondered, what about "to dumb down"? We know what the phrasal verb means but to the best of my knowledge "to dumb" doesn't exist as a verb on its own so here we have a phrasal verb where there is NO main verb. Or am I missing something? Are there any other phrasal verbs where the head word ISN'T actually a verb?

You have a combo here: a verb created from an adjective used to form a phrasal verb. This link notes many verbs created from adjectives (like “muddy” the waters, “perfect” your golf swing, & more), & also lists a few phrasal verbs made from them. Besides “dumb down,” there’s “tough it out” and “rough someone up.”

That sounds right, bethree, but somehow I've never liked "to dumb down," for the reason Bob states. It just doesn't exist. Rough someone up or tough it out just seem more reasonable.

M-W lists both dumb and dumb down as verbs. It dates dumb down to 1933.

The OED Online lists both as verbs and dates dumb down to 1927. It also lists dumb up from 1927, with essentially the same meaning as dumb down.

Word Spy lists a different meaning for dumb up: “To make an item seem more highbrow by adding token cultural artifacts; to raise one’s intellectual and cultural values.”

Interesting that dumb down has only been in use since 1933.