Great surprise at something remarkable or seemingly incredible.
Great surprise at something remarkable or seemingly incredible — often enough to stun or leave one speechless.
A heightened pitch of surprise: what astonishes is its sheer remarkableness, not merely its being unforeseen — the thing strikes one as almost beyond belief. Its “thunderstruck” root lends a stunned, momentarily-halted quality. It tilts toward the stunning, scarcely-credible pole, where amazement tilts toward bewildered admiration (a sense of not grasping how); a shade milder than being astounded, which leaves one at a loss what to think.
From astonish (c. 1300 astonien, “to stun, strike senseless”), from Old French estoner, from Vulgar Latin extonare “to leave thunderstruck” (ex- “out” + tonare “to thunder”).
The verb's original force was literal stunning (“strike senseless,” c. 1300); the softened emotional sense (“amaze, shock with wonder”) is from the 1610s. Current use has largely shed the “struck senseless” literalness. No reliable recent-generation shift.