Homonyms are very common in modern Chinese. Confusion of homonyms could be a disturbing problem in a conversation, for example, if you use “饭桶” incorrectly, you could offend someone.
饭桶 literally means “a rice bucket”, but it also has a figurative meaning, “someone good for nothing; a person of little worth or usefulness”.
The key to using 饭桶 properly:
When you say somene is a 饭桶, it carries the figurative meaning. Don’t call someone a 饭桶 unless you want to offend him/her intentionally or you get very angry.
Examples:
“Do not sit about like a lazy, good-for-nothing!” Don’t just sit about and dream! 别呆坐着像个饭桶一样！不要只是呆坐着梦想！
He who knows nothing but pretends to know everything, is indeed a good-for-nothing. 不懂装懂永远是饭桶。