The term 'letter opener' can be broken down into several crossword solutions. These include 'SIRS' (4 letters), 'MADAM' (5 letters), 'SIR' (3 letters), 'FLAP' (4 letters), 'STEAM' (5 letters), 'ALPHA' (5 letters), 'ADDRESSEE' (9 letters), 'DEAR' (4 letters), 'DEAREST' (7 letters), 'ELL' (3 letters), 'MESSRS' (6 letters), 'TOWHOM' (6 letters), 'DEARSIR' (7 letters), 'DEARSIRS' (8 letters), 'MAILDROP' (8 letters), and 'PAPERKNIFE' (10 letters). A letter opener is a tool used to open envelopes, typically made of metal or plastic. It is also known as an envelope slitter, paper knife, or letter slitter.