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1.
US Navy slang term for "Insert Foot In Mouth," normally pronounced "Effin IT," which mostly applies to 1st Lieutenants most of the time.)

Also pronounced as "Effining It" or "Eff It."
Bossum just IFIM it in front of the XO about the Captain's Herpes problem.

You just IFIM It, Mister. You're going up the Mast for Mutiny.
by Gunners Mate June 30, 2005