What is "word-addressable"

Word-addressable is a Computer Architecture term.

In computer architecture, a word is an ordered set of bytes or bits (typically 4 bytes(=32 bits)) that is the normal unit in which information may be stored, transmitted, or operated on within a given computer.

If a computer's memory is word-addressable then each word in memory is assigned its own memory address. That means that the processor is able to address and fetch only complete words from the memory.

Typically, if a processor has a fixed-length instruction set, then the instruction length equals the word length.