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.