Anybody who has ever had a protracted argument will have discovered that different people often mean something different when using a given word.
This can be quite frustrating for all involved. Hence a great deal of effort is invested in creating standardised meanings. From dictionaries, through programming languages, into philosophy and mathematics a standard refrain is to "define your terms" before building an argument/theory/conversation.
Unfortunately, it is impossibly difficult to unambiguously associate a specific meaning with a specific word.
So... I'm saying that the meaning of words can't be defined. And yet I'm using words to explain why the meaning of words can't be defined.
Obviously individual words do have meaning for each of us - but that meaning is subjective. The meaning of words depends on the relationship we have to those words. Again, it is relationships that provide meaning - not an inherent quality of the word itself - but our relationship (experience) with any given word. We then combine those relationships with each word into a new relationship within a sentence that conveys new information (a new pattern of relationships).
Miscommunication is common because nobody has an identical set of relationships with a given word. Communication is possible because our experience of (at least some) words is sufficiently similar that there is commonality between my set of relationships and your set of relationships for a word.
We can't define what an integer is. We can't define what the integer '1' is. However, the concept of 'one' is so common that we have an extensive network of things related to 'one'. It is the depth and breadth of relationships that gives us the sense that we understand what the numeral '1' represents even while we cannot specifically define the symbol.
(Mathematics has tried very hard to define anything/something. For further reading see The Foundational Crises in Mathematics).