Having “elbow room” basically means that a person either has enough space to move around in or to perform an operation or task in. The term doesn’t have to relate to physical space; it can also refer to intellectual space or freedom. In this sense a person could refer to the limitations of an essay topic as providing very little elbow room, meaning that the title or guidelines prohibit him or her from discussing anything outside the limited scope of the title.
"Elbow room" is an idiom, which is a small phrase that has a meaning not literally related to the words it is made up of. For example, the idiom “a leopard cannot change his spots” doesn’t literally refer to a leopard’s inability to change the color of its spots, but to people who are unable to change who they are. Many idioms are used in the English language, and this can be a particularly difficult part of the language for non-native speakers to understand. Most idioms are in some sense metaphorical, meaning that they use phrases related to a certain field to describe something not related to that field.
Unlike many other idioms, the phrase “elbow room” is often used in a virtually literal context. It is often said to literally mean space, although not necessarily room for the elbows, specifically. An instance where elbow space is an issue is at a dinner table, but the phrase has been expanded to mean space as a whole. For example, if somebody was looking around a house that they were considering moving into, they could state that the hallway didn’t have much elbow room if it were cramped in space. Likewise, the phrase can also be used to say that a location has abundant space to perform a certain task, as in “This office has plenty of elbow room.”
As the phrase gained popularity, it also took on another meaning that is related to having space. Elbow room can also be used to refer to intellectual space, or scope to perform a certain task. If somebody has been instructed to think about a problem in one specific fashion, they may think that they have no intellectual freedom to solve the problem. This is another instance in which a person could say that he or she has no elbow room.