Add words to Spell Check?

[billy]

I have found there's common "X10" words that "Spell Check" doesn't know.
Is there anyway to update the dictionary?

Words like :
sendrf
sendplc
transceive
PLC

[steven r]

How about starting with adding "AHP"?
Perhaps some common abbreviations like "HC".

A lot of times I just use ieSpell. It doesn't work any better for the above but it handles some of my typos better. I've seen this spell checker incorrectly attempt to fix the words.