(1)突然の思いがけない危機(通例危険を伴う)で緊急な行動をとる必要があること
(2)a sudden unforeseen crisis (usually involving danger) that requires immediate action; "he never knew what to do in an emergency"
さらに詳しく
(1)身体的または神経質の緊張の状態にある
(2)in or of a state of physical or nervous tension