Antonyms for the phrase "throws in to" include "withdraw," "conclude," "cease," "wrap up," and "finish." Each of these antonyms implies that something is being completed or ended, rather than added to. For example, if someone was "throwing in to" a conversation, they might withdraw from it by saying they have to leave. Alternatively, they might conclude the conversation by summarizing their thoughts and saying goodbye. If they were to cease throwing things in to the conversation, they might instead simply listen to what others have to say, or they might wrap up the discussion by making a final point before moving on.