Green’s Dictionary of Slang

Met n.

[abbr.]

1. [late 19C–1910s] the Metropolitan Music Hall, London.

2. [late 19C+] the Metropolitan Railway, part of the London Underground system.

3. [late 19C+] (US, also Mett) the Metropolitan Opera House, New York; also attrib.

4. [1940s+] (also Mets) the Metropolitan Police, serving London.

5. [1940s+] the Meteorological Office, responsible for weather forecasting; usu. as the Met Office; thus Met man, a weather forecaster.