What does the word "characterize" mean in an EE context?
Starting at the beginning,


  Simple Definition of characterize
  
  : to describe the character or special qualities of (someone or something)
  
  Source: Merriam-Webster's Learner's Dictionary


This is one of two basic definitions for characterize (which describes the action you are referring to).

I think this definition makes a lot of sense, in context, but coming at it from the other direction, an instrument or device or circuit that is NOT characterized has not been studied and described in a way that may be necessary to understand its fundamental characteristics.

In general, there are two categories of device that the EE can deal with.. one that is characterized sufficiently.. ie one that is understood well enough to utilize for some purpose -- but not necessarily totally understood.

...and one that is NOT characterized sufficiently. You may characterize a resistor as Red Black Black Gold by visual observation. You understand that to be a 20 Ohm 5% resistor, and have a reasonable belief that the marking is accurate. But if you need a 1/2 watt resistor, but are unsure of what you have, it is not sufficiently characterized.

You may characterize it by putting a certain amount of power through it and observing the temperature rise... eventually deciding that 1/2W through the resistor raises the case temperature 40C, and that this is sufficient in your application.

NOW the resistor is fully characterized to your need.




  "Why would a EE invest time in characterizing a device or instrument?"


If the EE does not fully understand the specification of the device or instrument, or the needed information isn't published as a specification, the EE needs to do work to determine if that device or instrument will work in the needed application.


  "What would be his or her primary objectives in doing so? What outcomes, once achieved, would cause them to stop characterizing, considering their objectives achieved?"


Generally this is a test for suitability. Once these questions have been answered (is this device suitable: yes or no?) it's probably time time to stop.


  "In what ways am I already naturally occupied by characterizing devices, circuits, or whatever, just that I'm not using that word to describe what I'm doing?"


Any time you seek to understand a device or a circuit in a situation that isn't fully given by its documentation, a characterization step probably is taking place -- especially if that effort involves testing.