Is there a term for 'a three-syllable word with stress on the second syllable'? (Or similar)

Solution 1:

Words whose stress is on the penult are called paroxytone words per Oxford Dictionaries Online.

Since this can be used as both an adjective and a noun, you are talking about trisyllabic paroxytones. I normally use the -ic version for the adjective, so paroxytonic.

There are also oxytonic words stressed on the last syllable and proparoxytonic words stressed on the antepenultimate syllable.

Solution 2:

Amphibrach.

"Gazebo is an amphibrach" i.e. it has three syllables and has its stress on the second/middle syllable.

"Elephant is a dactyl" and "Employee is an anapest".

https://en.wikipedia.org/wiki/Amphibrach

Solution 3:

Perhaps amphibrach.

According to Wikipedia, "in English accentual-syllabic poetry, an amphibrach is a stressed syllable surrounded by two unstressed syllables." I'm not sure if it is used outside of poetic contexts, though. An amphibrach does not have to be a single word, and its boundaries don't have to correspond to word boundaries.

It's one of many such terms taken from the names given to metrical feet in antiquity. Another one, the bacchius, is mentioned in the answer to the following question: What is the name of a particular poetic foot, unstressed, stressed, stressed?