As a Noun:
1. A single unit of language that is uttered in speech. English = word.
2. A single unit of language that can be represented in writing or speech. In English, it has a space on either side of it when it is written. It can have one or more meanings. English = word.
As a Verb or Adjective:
1. To utter a single unit of language in speech; to say a word.
2. To communicate in language using words, rather than signs.