There are several synonyms for the phrase "about twenty" that can be used when referring to a quantity or number that is approximately 20. Some of these synonyms include "around twenty," "roughly twenty," "nearly twenty," "just about twenty," "almost twenty," and "approximately twenty." These phrases can be used interchangeably and are commonly used in everyday conversation and writing when an exact number is not necessary or known. It is important to note that while these phrases indicate an approximate number, they do not provide an exact number, which may be needed in certain contexts.