How we cite our quotes:
Under your patience, gentle empress,
'Tis thought you have a goodly gift in horning;
And to be doubted that your Moor and you
Are singled forth to try experiments:
Jove shield your husband from his hounds to-day!
'Tis pity they should take him for a stag. (2.3.1)
When Lavinia says Tamora has a reputation for being good at "horning," she means it as an insult. Horning refers to the way a promiscuous woman can make her husband a "cuckold" (a man who's been cheated on). In Shakespeare especially, "cuckolds" are often said to have horns like monsters or animals. The idea is that a cheating woman has the power to transform her husband into something disdainful.
Believe me, queen, your swarth Cimmerian
Doth make your honour of his body's hue,
Spotted, detested, and abominable.
Why are you sequester'd from all your train,
Dismounted from your snow-white goodly steed.
And wander'd hither to an obscure plot,
Accompanied but with a barbarous Moor,
If foul desire had not conducted you? (2.3.2)
We talk about this quote under "Race," but it's worth mentioning here as well. When Bassianus and Lavinia find Tamora alone in the woods with a "barbarous Moor," they declare that her "honour" has been blackened by her sexual relationship with Aaron. (In Shakespeare's work, the term "Moor" or "blackamoor" usually refers to a black man or woman.)
Unfortunately, we see this kind of thinking throughout 16th century literature, which tends to portray black men as being capable of contaminating white women. (Consider, for example, Othello, a play in which several characters worry that Desdemona has been soiled by her marriage to Othello.)
Farewell, my sons: see that you make her sure.
Ne'er let my heart know merry cheer indeed,
Till all the Andronici be made away.
Now will I hence to seek my lovely Moor,
And let my spleenful sons this trull deflow'r. (2.3.13)
Here Tamora announces that she's off to have a dalliance with Aaron while her sons rape Lavinia in the woods. By now it's clear that the play associates Tamora and Aaron's adulterous affair with the ugliness of desire.