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1. supposably
A series of phonemes commonly uttered by English language speakers who share a common defect in English language acquisition.
When asked if she had received competent English language instruction, Alberta replied "supposably."
2. Supposably
Fictional word that mentally retarded persons often confuse with the word "supposedly".
Ignorant Person: "Casey Anthony supposably killed her daughter Caylee."

Smart Person: "Supposably is NOT a word you fucking idiot."
3. supposably
It actually is a word: capable of being conjectured or imagined.

This word was popularized in an episode of Friends in the second season.
Did they go to the zoo?
Supposably...