Q:

What's the meaning of "brutal" here?

What's the meaning of brutal in this comment?

I just had some mild food poisoning on Tuesday into Wednesday, sh-t was brutal but it was pretty much cleared up after I slept. 

According to most dictionaries, the word brutal has three senses. The following are definitions of brutal from Google definitions:

adjective /ˈbro͞otl/ 

Savagely violent - a brutal murder
Punishingly hard or uncomfortable - the brutal winter wind
Without any attempt to disguise unpleasantness - the brutal honesty of his observations

Although definition #2 seems relevant, but based on the dictionaries I've looked up, its usage appears specifically applies to the weather. So how do you define brutal in this context?

A:

From the American Heritage Dictionary, under brute, I fount a few synonyms that may be helpful:  "entirely physical: brute force; savage, cruel: brute coercion; and unremittingly severe: was driven to steal food through brute necessity."  
While something brutal may be entirely physical, as in the case of our food poisoning victim, it can also, by analogy, be mental.  The feeling engendered by, say, the bar exam, might leave you feeling spent, as if you had been through a purely physical test; hence, "Now that was a brutal exam!"    
Savage describes the symptoms of food poisoning.  It has no mercy.  Retching and the dry heaves are truly savage in their paroxysms or attacks on our bodies.
Unremittingly severe describes the symptoms of food poisoning as well.  There is a witty saying to the effect that "At first I was afraid I would die; then I was afraid I would not die!"  

