Answer:
Simile.
Step-by-step explanation:
A simile is a figure of speech that compares two qualities using the word 'like' or 'as'.
The phrase "as strong as an ox" is a simile as it compares the strength of someone to that of an ox.
Another example of a simile is "John is as slippery as an eel", here too, the speaker is not saying John is an eel but is comparing John's quick wit to an eel, because an eel is not easy to catch.