The phrase "stick one's neck out" is an idiomatic expression that refers to taking a risk or being brave enough to take a stand, especially in a challenging situation. The antonyms or opposite words that can be used for this expression are "stay in the background," "remain cautious," "play it safe," or "keep a low profile." These words indicate that a person is not taking any bold action, instead they are following the traditional rules and not stepping out of their comfort zones. Consequently, sticking one's neck out can be seen as a positive thing, but it requires some level of courage and a willingness to accept the risks involved.