"Topful" is a rarely used word that means "completely full to the top". There are several synonyms that can be used in place of "topful", depending on the context. Some of these synonyms include "overflowing", "brimming", "bursting", "crammed", "jammed", "packed", "chock-full", "teeming", "abundant", "plethora", "plentiful", "overflowing", "replete", "satiate", "saturated", "surfeited", "swarming", "thronging" and "crowded". These synonyms can be used interchangeably to convey the message of fullness or abundance, and help writers and speakers to add more variety to their language.