Definition of "EF"

(medicine, cardiology) Initialism of ejection fraction.

(computing, Microsoft) Initialism of Entity Framework, an open-source ORM framework.  examples

(Canada, US, meteorology) Followed by a number from 0 to 5: initialism of Enhanced Fujita, a rating on the Enhanced Fujita scale used to indicate the intensity of a tornado. It has superseded the Fujita scale.

(Roman Catholicism) Initialism of Extraordinary Form.  examples

(philately) Initialism of extremely fine or extra fine; also XF.  examples