When someone uses the eggplant emoji they are usually meaning sex.
In text and chat the eggplant emoji stands for a penis because the eggplant is in the shape of a mans penis and when the eggplant emoji is followed by or paired with the mouth emoji it means oral sex.
Then when the eggplant emoji is paired with the peach emoji or paired with a butt or female genitalia, it means anal or vaginal sex.
So when someone uses the eggplant emoji in a text or chat to you then they are saying something about a penis and possibly sex.
It all depends on what they are saying afterwards or with the emoji.
However I've used the eggplant emoji to tell my husband to pick up some eggplants for a recipe that I was needing them for.
So if it's just the eggplant emoji by itself it could simply mean an eggplant.