1. When an asian person has been out of the presence of people for a long time.
2. Can also be used with any other race. I.e incognegro (african americans), incogcasian (caucasians), incogbeaner (mexicans). etc.
"Yohnny, why have you been incogasian?"
"I've been incogasian becuase I've been working on this really hard math problems."