Sentence:  Then of a sudden she was kissing and fondling instead of fighting me off, laughing under her breath and using a few horny words I didn't know at that time; presently her hands were gripping her knees, I was in her standing, joyfully <WSD>stallionizing</WSD> it with not a thought in my head to interfere. 
Meaning of the word marked with <WSD> tags:  To behave like a stallion, especially to engage in sexual intercourse.