RE: Definition

You put forth an interesting question, Hayley, though a difficult one. Putting a definition on something, as you say, is very limiting, so let us try to define this profession as broadly as possible so as to give ourselves room to grow and change. First, let's look at each word separately.

technical

1.	belonging or pertaining to an art, science, or the like: technical skill.

2.	peculiar to or characteristic of a particular art, science, profession, trade, etc.: technical details.

3.	using terminology or treating subject matter in a manner peculiar to a particular field, as a writer or a book: a technical report.

4.	skilled in or familiar in a practical way with a particular art, trade, etc., as a person.

communication

1.	the act or process of communicating; fact of being communicated.

2.	the imparting or interchange of thoughts, opinions, or information by speech, writing, or signs.

3.	something imparted, interchanged, or transmitted.

4.	a document or message imparting news, views, information, etc.

-- dictionary.com

When I think of the word "technical," I think of something that requires specialized knowledge. This could be almost any discipline, from medicine to computers to the environment. Even what I do (edit social studies textbooks) requires specialized knowledge. Though I don't think of myself as a technical communicator, per se, my job seems to fit under that description.

And "communication" obviously covers a wide range of media: brochures, manuals, books, magazines, press releases, newspapers, websites, blogs, speeches and presentations, and even textbooks.

So I suppose my best stab at a definition would be:
Technical communication is the act of imparting specialized information to a given audience through a wide array of media.

Can I get any more vague?