Entry 1 sense Webster, 1913 Sea adder /sē ăd'-ẽr/ · Sea· ad·der · IPA 01 The European fifteen-spined stickleback (Gasterosteus spinachia); -- called also bismore. 1. The European fifteen-spined stickleback (Gasterosteus spinachia); -- called also bismore.(Zool.) Also: bismore