From the word milf (mother i'd like to fuck), coined by the American Pie movies.
Used to describe a horse that you find incredibly delectable and would love to have sex with.
Can be said by both men and women, but in the case of women sex with a horse has been known to cause massive internal bleeding, normally resulting in a slow and painful death.
2.'Look at that girl on that horse. I wish she'd fuck off so that i could that HIlF a good riding!....Then i'd bang her too.'