to stay where you are rather than moving away or changing position; to stay in the same situation, without changing your mind or taking any action
Oxford61% of films
to stay where you are rather than moving away or changing position
Sit tight, Blue One, we're inbound to your pos.
Like, sit tight, old buddy.
Oxford39% of films
to stay in the same situation, without changing your mind or taking any action
Okay, at this very moment, I say we sit tight and assess.
Definitions from the Oxford Advanced Learner's Dictionary, 9th edition