suddenly and unexpectedly; "rain caught them unawares"; "sorrow comes to all, and to the young it comes with bittered agony because it takes them unawares"- A.Lincoln
without forethought or plan; inadvertently; "came upon the diamond unawares"
(bridge) a playing card with a value sufficiently high to insure taking a trick in a particular suit; "if my partner has a spade stopper I can bid no trump"
close or secure with or as if with a stopper; "She stoppered the wine bottle"; "The mothers stoppered their babies' mouths with pacifiers"