Asking him to define that is comparable to asking him to talk about his feelings, something he goes out of his way to prevent people from realizing he has. It's a defense mechanism, a survivor's skill, something that's kept him alive far longer than the rest of his race. Vegeta's cold nature isn't the default for Saiyans, just the shape he molded himself into as a result of traumatic experiences at a young age and a desire to survive in the face of impossible odds.

And while he does trust Bulma to a degree — arguably, she's the only person he trusts, as how much he chooses to trust Kakarot depends on the day and situation — he's not yet at the point where he's willing to let walls he's held in place since childhood down. Especially not when he's barely voiced interest, let alone clear intent.

He snorts. "You wouldn't understand, even if I did."