So what does regnant mean - no it's not what happens to people when they produce offspring. Regnant is to exercise authority or rule.
The following is the official dictionary description of the word:
1. reigning; ruling (usually used following the noun it modifies): a queen regnant.
2. exercising authority, rule, or influence.
3. prevalent; widespread.
1590–1600; < Latin rēgnant- (stem of rēgnāns ), present participle of regnāre to rule; see reign, -ant
I'm not sure what attracted me to this word as the meaning and origin of the word is really not anything all that interesting. I think it's just the fact that the word is pregnant with the "p" removed. Interesting how adding a "p" to the beginning of this word completely changes it's meaning.