The quality or state of being giddy; dizziness, lightheadedness, or frivolous excitement.
From giddy plus the noun-forming suffix -ness, which creates abstract nouns from adjectives (like happiness from happy, sadness from sad).
The -ness suffix is English's favorite way to turn feelings into countable concepts—you can talk about giddiness the same way you'd discuss sadness or happiness, making emotions into things you can study.
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