Here is the 1828 definition of "insurrection", not that it matters, because Congress can define it however they like and claim he committed "insurrection" even with no evidence and there is no recourse:

INSURREC'TION, noun [Latin insurgo; in and surgo, to rise.]

1. A rising against civil or political authority; the open and active opposition of a number of persons to the execution of a law in a city or state. It is equivalent to sedition, except that sedition expresses a less extensive rising of citizens. It differs from rebellion, for the latter expresses a revolt, or an attempt to overthrow the government, to establish a different one or to place the country under another jurisdiction. It differs from mutiny, as it respects the civil or political government; whereas a mutiny is an open opposition to law in the army or navy. insurrection is however used with such latitude as to comprehend either sedition or rebellion. It is found that this city of old time hath made insurrection against kings, and that rebellion and sedition have been made therein. Ezra 4:19.
2. A rising in mass to oppose an enemy. [Little Used.]

It should be impossible to prove since there was no inciting. But, well...

What worries me a bit about this one is it only requires a simple majority vote to pass in the house and senate.