Final answer:
In Othello, 'the beast with two backs' refers to sexual intercourse between Othello and Desdemona, a term used by Iago to dehumanize Othello.
Step-by-step explanation:
In the play Othello, the phrase 'the beast with two backs' is used by Iago to describe sexual intercourse between Othello and Desdemona. It is a crude term used to emphasize the physical, primal nature of their sexual relationship. Iago uses this phrase to dehumanize Othello and to plant seeds of doubt and suspicion in the minds of others.