1. [1930s+] (orig. US) involved with, concerned about, believing in.
2. [1950s+] (US black) as a result of, as a consequence of, in reference to.
3. [1960s+] (orig. US) in full understanding of.
4. [1970s] (orig. US) excited by, obsessed with.
1. [late 19C] (US) to start smoking or drinking.
2. [1900s; 1960s+] to make a commitment to an idea, a job, a person etc.
3. [1970s+] (also groove behind) to understand, to enjoy, to appreciate [groove v. (2)].
SE in slang uses
[1980s+] (US) to any extent, under any circumstances; usu. in phr. I wouldn’t trust (someone) behind a dime.
see back of God speed under back adv.
[1950s+] (UK prison) locked up in solitary confinement; also as an order, behind your doors! get into your cell!
[late 19C] out of date, out of fashion, not up with the latest situation.
[20C+] (W.I.) begging, harassing, pressurizing.
[1920s+] (orig. US black) old-fashioned, passé.
[1980s] a phr. describing anyone in authority, esp. a police officer or prison warder.
[1980s+] (US black) a drug seller’s place of business, thus the weighing and selling of the drug.
[20C+] (US Und.) in prison.
[1940s] (US black) to argue with something, to contradict the facts.