Source : Free On-Line Dictionary of Computing

return from interrupt
     
         (RTI) An instruction {mnemonic} on many
        computers including the {6502} and {6800}.  The variant "RETI"
        is found among former {Zilog Z80} hackers (almost nobody
        programs these things in {assembly code} anymore).  The {Intel
        80x86} equivalent is "IRET".
     
        (1994-10-31)