"Flea bag" is a derogatory term used to describe someone or something that is dirty, messy, or unkempt. There are many synonyms that can be used in place of this unpleasant term. Some of the most common include "squalid," "filthy," "grimy," "unclean," "dusty," "dingy," "musty," "sordid," "muddy," and "disheveled." Other less common options include "unhygienic," "unkempt," "seedy," "untidy," "unwashed," "grubby," and "shabby." Whether you are describing a run-down hotel room or criticizing someone's appearance, there are plenty of ways to convey the same idea without resorting to offensive language.