It applies to both men and women. It indicates sexual excitement and a desire for sexual activity, but not necessarily a willingness or consent to it.

if sb says he or she is horny,that means he or she wants to have sex now

The definition of horny ... is simply another word for being hungry for love. "I am horny for you" means precisely "I am hungry for your love" - vs hungry for love in general. "I am horny for you" thus means I am ready to be loved BY you and I am ready to GIVE love to you - i.e. to make love with YOU. James Joyce even used the term in his Ulysses. This word was first recorded in 1889.

It comes from the old expression, "to have the horn" (in your pants). It applies to both guys and girls nowadays.

shotrly , a person who wants have sex like what courtney said ,