of all meaning
EN- AdverbSUF-all
- Used as an intensifier with superlative forms of adjectives.
- Best of all was the bicycle I got.   First of all, I'd like to thank my agent.   He was the greatest playwright of all.
- Used as an intensifier with nouns to denote being ultimate.
- Of all the queer collections of humans outside of a crazy asylum, it seemed to me this sanitarium was the cup winner. […] When you're well enough off so's you don't have to fret about anything but your heft or your diseases you begin to get queer, I suppose.
- Used as an intensifier with superlative forms of adjectives.
- More Examples
- Used in the Middle of Sentence
- Hmmmm...I don't know about the combo...I've never tried that...but I love Xans and Valiums...well until I OD'd on Valiums and almost died...now I'm afraid of all pills...
- Either Bart Starr or Brett Favre was the greatest Packer of all time.
- The most famous Broadway theatrical revues of all time were the Ziegfeld Follies.
- Used in the Beginning of Sentence
- Of all the tickets 65 percent went to tourists, and 18 percent to surburbanites.
- Of all Infirmityes belonginge to us I hould those woorst that will not lett a man Rest in his bedd a-nights.
- Of all the Waldorf salads I've tasted, this is the finest.
- Used in the Ending of Sentence
- He is at most a confus'd and wild Christian, not specializ'd, by any forme, but capable of all.
- Used in the Middle of Sentence
Definition of of all in English Dictionary
- Part-of-Speech Hierarchy
- Phrases
- Prepositional phrases
- Prepositional phrases
- Adverbs
- Prepositions
- Prepositional phrases
- Prepositional phrases
- Phrases
Source: Wiktionary
Grammatically, this idiom "of all" is a phrase, more specifically, a prepositional phrase. It's also an adverb. It's also a preposition, more specifically, a prepositional phrase.