Expression: "Out in left field mean"

[Tom]

Hi

Could you please tell me if the expression given below is an idiom or what? What does it really mean? Is it common in everyday English?

Out in left field mean

Tom

[Yankee]

Hi Tom

Yes, that expression is very well-known in the US.
You can find it here (scroll down to left field)

His plan was really out in left field. (His plan was strange or out of touch with reality.)
His criticism came out of left field. (The criticism was unexpected.)

The preposition between out and left field sometimes changes. And sometimes the word way is used before out to indicate extreme strangeness:

way out in left field

What was the sentence/context you found this in?

Amy

[Tom]

[Tom]

[Yankee]