The term "lid" has multiple meanings depending on its context.
1) In a general sense, it can refer to any cover or top that is used to close or seal something such as a container, box, or tank. For example, you might say "I put the lid back on the jar."
2) It can also be used figuratively to mean a limit or restriction. For instance, someone might say "There's no lid on how much he can spend" meaning that there is no limit to how much money they can spend.
3) In some regions of England and Ireland, the term "lid" is used as slang for head, specifically referring to a person’s skull or brain case. For example, you might hear someone say “I gave him a good lid” meaning that they hit him on the head.