The phrase "that will do" is often used to indicate that something is satisfactory or sufficient. However, there are many other words and phrases that can be used in its place. Some synonyms for "that will do" include "good enough," "acceptable," "adequate," "satisfactory," "sufficient," "suitable," and "appropriate." Other options might include "it'll suffice," "that's fine," "that works," or "we can manage with that." Ultimately, the choice of synonym will depend on the context of the situation and the speaker's personal preference.