What type of fallacy is this?

The term "man" is being used as a general term and not specific. Maybe Equivocation.

fallacy of (the) undistributed middle.

A formal fallacy in a categorical syllogism where the middle term (mortal), or the term that does not appear in the conclusion, is not distributed to the other two terms. For a good explanation of what it means to be distributed, see https://en.wikipedia.org/wiki/Categorical_proposition#Distributivity