[John Doe] {n.} A name used for an unknown person, especially […]

[John Hancock] or [John Henry] {n.}, {informal} Your signature; your name […]

[John Q. Public] {n.} A name used informally for the average […]

[John Thomas] {n.} Penis.

[Johnny] {n.} Condom. Sometimes also a 'Johnny bag' or 'rubber Johnny'.

[Johnny-come-lately] {n.} Someone new in a place or group; newcomer; also: […]

[josser] {n.} A cretin or simpleton.

[judgment seat] {n.} A place where you are judged; a place […]

[juice dealer] {n.}, {slang} An underworld money lender who charges exorbitant […]

[jump] {n.} {v.} As a noun or verb, sexual intercourse.