Definition of giddy-up:
(adj) :
(predicative only) Feeling a sense of spinning in the head, causing a perception of unsteadiness and being about to fall down; dizzy.
(adj) :
(attributive) Causing or likely to cause dizziness or a feeling of unsteadiness.
(adj) :
(by extension) Joyfully elated; overcome with excitement or happiness.
(adj) :
(by extension) Unable to concentrate or think seriously; easily excited; impulsive; also, lightheartedly silly; frivolous.
(v) :
(transitive) To make (someone or something) dizzy or unsteady; to dizzy.
(v) :
(intransitive) To become dizzy or unsteady.