equestriess 

noun: A cross between a female equestrian and a princess.
Males should be adequately forwarned about the dangers of equestriess'. Bitches that ride horses scheme with one another due to inherent social/personal insecurities.
A 'princess' is a high-maintenance, spoiled brat.

Hence, a large percentage of the female equestrian population may be considered an "Equestriess".

Ex: The herd of females that arrived to our apartment last night included one equestriess... She successfully blocked my cock between the hours of 10pm and 3am.

equestriess by Neil Strauss of mystery February 26, 2011

Equestrienne 

A female equestrian, or a female horseback rider.

Edward Gal is an equestrian, and Debbie MacDonald is an equestrienne.

Equestrienne by GoDiva8 March 11, 2011

equestriaschlong 

Noun. 1) The large penis of a racing horse. 2) A penis comparable in size to the penis of a racing horse.

Coined at Poplicks.com: http://poplicks.com/2008/07/what-if-war-broke-out-over-condom-ads.html

Before Mary decided to saddle up to the stud, she made sure to pack some extra-large condoms that would fit his equestriaschlong.

equestriaschlong by Camilla Toe August 14, 2008