John Mayer got deep during a chat with Matthew McConaughey over the weekend ... revealing his definition of being in love.

Check it out ... the "New Light" singer said he knows he's in love when he can picture the person with him in "the most precious place" -- his imagination. Gallery Launch Gallery Getty

To keep it simple, if he can dream of his life with his partner in it ... that's when he knows he's in deep.

Seems like John hasn't been able to invite anyone into his beloved dream space for quite some time ... 'cause he hasn't publicly dated anyone for years.

He was last linked to "Chilling Adventures of Sabrina" actress Kiernan Shipka in 2022, and in June this year, he reportedly confirmed he's single -- and ready to mingle -- during a live event. Gallery Launc

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