(physics) A radioactive isotope of nitrogen, ¹³₇N, having seven protons and six neutrons, and a half-life of less than ten minutes; it is used in positron emission tomography

Alternative form of ROT13

(physics) the less common of the two stable isotopes of carbon, ¹³₆C, having six protons and seven neutrons

Alternative form of sweet thirteen

(US, military slang, dated) A trash can, wastepaper basket.

(organized crime) Mara Salvatrucha, a criminal gang operating in some Salvadoran communities in Central and North America.

suitable for adolescents, typically due to the absence of explicit sexuality and intense graphic violence

Alternative spelling of grade thirteen

plural of sweet 13

Abbreviation of thirteenth.