SE in slang uses
[1940s+] the second most important person, the second-in-command.
[1930s+] (US black/teen) sexual exploration above the waist (cf. first base n. (1); third base under third adj.; home run n. (2)).
see first chop adj.
[1990s+] (gay) the hiding of one’s specific sexual preferences and practices, even if the basic fact of homosexuality can be admitted; also used of domestic violence within same-sex relationships.
1. a worn-out prostitute.
2. an ageing passive homosexual.
[1910s+] (US) to follow a leader or someone first-rate, with the hope of advancement or promotion.
[2000s] the vagina.
[late 19C+] (US) a break-in, spec. one that involves climbing above ground level; also attrib.
[late 19C+] (US) a thief who climbs into buildings above the ground floor.