stamped addressed envelope
noun /ˌstæmpt əˌdrest ˈenvələʊp/,  /ˌstæmpt əˌdrest ˈɒnvələʊp/
  /ˌstæmpt əˌdrest ˈenvələʊp/,  /ˌstæmpt əˌdrest ˈɑːnvələʊp/
(abbreviation sae)
 (British English)- an envelope on which you have written your name and address and put a stamp so that somebody else can use it to send something to you- Please enclose a stamped addressed envelope to get your test results.