Assuming that you’re referring to “pulling information out of your ass”, you could try: “Pulling facts out of thin air” or “making it up on the go”. Getting more creative with it: “unscripted intellect”, “on the spot expertise”.

A real gentleman would probably say “conjecture” or “unfounded information”, but a less explicit word is “nonsense”

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Rectally sourced figure

Malarkey Nonsense Fabrication

An “ad hoc solution”?

Wingging it.

Pulled out of thin air

deus ex machina

Hexbear argument.

Amateur hour

Cut from whole cloth

i’m just spitballing here… i’m thinking perhaps… maybe… does this resonate… have you considered… from another perspective… possibly… informed opinion… its likely… in the ballpark of… something like…

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Made up on the spot.