- (organic chemistry) methyl ethyl ketone
- (surfing) The chemical methyl ethyl ketone peroxide which is used as a catalyst to harden the fibreglass resin in surfboard manufacture and repair. Strictly speaking the abbreviation would be MEKP, but the shorthand MEK is frequently found.
- 2007: The amount of MEK (methyl ethyl keytone peroxide) has an influence on the strength of polyester resin. — Harbour Surfboards 
- (organic compound): butanone