O chem is short for organic chemistry.

I am studying O-Chem this semester.

I am studying O Chem this semester.

O-chem is a branch of chemistry that focuses on the study of organic compounds.

I have a test on O-chem tomorrow.

She decided to try the O-shot to enhance her sexual pleasure.

O-Tsukimi is a traditional Japanese festival where people gather to admire the beauty of the moon.

He saw a man-o-war in the harbor.

I traveled to the back o' Bourke to experience the true outback of Australia.

I've never been to the back o' Bourke.