The phrase "put stopper in" implies putting an end to something, closing or plugging up an opening or passage. The antonyms for the phrase will vary depending on the context of use. In a literal sense, antonyms for "put stopper in" could be words associated with opening or allowing flow such as "open up," "uncork," "release," or "unplug." In a figurative sense, antonyms for the phrase could be words associated with continuing or allowing action such as "proceed," "continue," "uninterrupted," "unhindered," or "unrestricted." Overall, the antonyms for "put stopper in" suggest an opposite direction or approach to what the phrase itself implies.