It is often said that "meaning is context".
This is a hollow definition because the context has its own meaning, which is its wider context, and so on until all contexts have been exhausted. It is the same recursive issue as the dictionary problem, where every word is defined in terms of other words and there is no a priori vocabulary which a dictionary can call on. The whole game depends on a level of existing knowledge obtained by the reader from elsewhere. Similarly, there is no a priori context to give meaning to anything which can provide further context; the thinker must already have a baseline of knowledge.
What approaches to meaning have philosophers taken to get round this problem?