Common in the fields of gametype-making, map-making and strategy-planning.
The usage of "terst" was, for a long time, of a somewhat esoteric nature. One could walk the interweb and hear echoes of
"terst" bounce in the great halls.
However, the roots of "terst" lies in the realm of Halo 2 online-playing.
A wave of Gametypes measuring a certain level of awesomeness all seemed to have "terst" in their names, and the hearts of many bright players embraced this connection and began using the word as a tribute to all that is genius.
With fierce speed, the word made it's way to all of interweb and today it is recognized as a respected symbol of
really good planning/thinking and/or
"What you did just now, that was terst!"