The pursing of one's nose so that it resembles that of a Llama. The nostrils will also arch, and harden due to the pursing. The upper lip will usually also tend to elongate downwards slightly adding to the Llama effect.
To attempt this you simply do your best to purse/flex/harden your nose, flaring your nostrils and upper lip.
Once this is mastered, you can for example use a seductive look whilst licking your lips to look like the "deviant Llama" or get all starey eyed, and look back and forth really fast to do the "nervous or scared Llama".
A: Hey sis, I think that guy over there is doing the Llama Nose.
B: Nah, see he's like that all the time, he's a freak.
A: Well check out this crazy Llama *purses nose and stares at sister*.