Adjective

(er)

Dizzy, feeling dizzy or unsteady and as if about to fall down.

The man became giddy upon standing up so fast.

Causing dizziness: causing dizziness or a feeling of unsteadiness.

They climbed to a giddy height.

Lightheartedly silly, or joyfully elated.

* {{quote-book, year=1905, author=

, title= , chapter=2 citation , passage=Miss Phyllis Morgan, as the hapless heroine dressed in the shabbiest of clothes, appears in the midst of a gay and giddy throng; she apostrophises all and sundry there, including the villain, and has a magnificent scene which always brings down the house, and nightly adds to her histrionic laurels.}}

The boy was giddy when he opened his birthday presents.

(archaic) Frivolous, impulsive, inconsistent, changeable.

* 1599 ,

In brief, since I do purpose to marry, I will think nothing to any purpose that the world can say against it; and therefore never flout at me for what I have said against it, for man is a giddy thing, and this is my conclusion.

* 1784 , , Tirocinium; or, A Review of Schools

Young heads are giddy and young hearts are warm,

And make mistakes for manhood to reform.

Adjective

(wikipedia undefined) (-)

Lacking a definition or value.

(mathematics, computing) That does not have a meaning and is thus not assigned an interpretation.

The result of division by zero is undefined .