boggle

(noun): A scruple or objection.
(noun): A bungle; a botched situation.
(verb): Either literally or figuratively to stop or hesitate as if suddenly seeing a bogle.
(verb): To be bewildered, dumbfounded, or confused.
(verb): To confuse or mystify; overwhelm.
(verb): To embarrass with difficulties; to palter or equivocate; to bungle or botch.
(verb): To dissemble; to play fast and loose (with someone or something).

The dogs went on, but the horse boggled at the sudden appearance of the strange beast.
He boggled at the surprising news.
The oddities of quantum mechanics can boggle the minds of students and experienced physicists alike.