27. Onion slang

The word 'onion' is used in many different ways as slang, mostly related to drugs.

For example; An Onion of Weed?
"I'm picturing a blooming onion made with weed butter."

Rapper Big L made the hip-hop track Ebonics in which he "break this slang shit down".
In the lyrics you can read the following sentence:
"Taking orders is sonnin', an ounce of coke is a onion"

"Another "confuse the police" slang term that is no longer used. These types of slang terms have to be changed frequently because the authorities eventually catch on to their meaning. They also have to be vague to avoid detection. Onion is slang for ounce because they share the same first letter. The term onion is used because when you hold it in your hand, it is shaped like an onion (or a softball, which is also a slang term) Currently "onion" is more likely to be used to describe the shape of a woman's ass, or an ounce of marijuana."

Here and here you can find a lot more meanings.

"Someone who goes against the consensus of a group, generally used in political or intellectual discussions."
Person 1: "I love this book."
Person 2: "Me too."
Person 3: "It's not that great"
Person 1: "You are the onion of the group!"