the act of spewing opinionated gibberish by one who doesn't know what the fuck they're talking about

1) Lacking knowledge.

2) Slang: Insult used to describe another party as stupid and/or prejudiced. Often used incorrectly as the most ignorant parties in a debate tend to call others ignorant to make up for their own lack of information or prejudices.

How ignorant people spell the word 'ignorant'.

Being uneducated on specific subjects.
Actually most of these definitions are written by ignorant people, who shouldn't be giving "definitions" to others.

I thought I thought I knew a thing and knew the thing was true, but as I learned and time went on I gradually grew, and learned the things I thought I knew were really only thoughts, and all the things at times just thoughts entirely for naught, knowledge is a fickle thing and like the brain in grams, that weigh themselves upon the mind and shape the way it scans, for better or for worse and hopefully for better things, you'll learn to know what really is and keep the thoughts just things.

Lack of knowledge

Lacking in knowledge, awareness, empathy, and wisdom. Can apply to anyone, regardless of political affiliation. Contrary to popular belief, it is a very broad state of mind, not largely dependent on one's specific views on a subject. Despite this larger meaning, this word is usually hurled towards others by people who are also ignorant who happen to be upset by something someone said.