electro-acoustic transducer for converting electric signals into sounds; it is held over or inserted into the ear; "it was not the typing but the earphones that she disliked"
a plant having a life cycle that normally takes two seasons from germination to death to complete; flowering biennials usually bloom and fruit in the second season
having a life cycle lasting two seasons; "a biennial life cycle"; "parsnips and carrots are biennial plants often grown as annuals"
occurring every second year; "they met at biennial conventions"
being of crucial importance; "a pivotal event"; "Its pivotal location has also exposed it to periodic invasions"- Henry Kissinger; "the polar events of this study"; "a polar principal"