If a word conforms to a special rule, I call it an Outside Word™.
Use the examples below to find the rule. I have made a mistake with a few of the words, so I've marked them with an "(E)" for error, while leaving them in so as not to invalidate Deusovi's correct answer.
|Outside Words™||Not Outside Words™|
And, if you want to analyze, here is a CSV version:
Outside Words™,Not Outside Words™ FEED,STARVE HEN,ROOSTER DIRE,TIRE SEND,SENT SQUISH(E),SQUASH GREEN,BLUE HEX,CURSE WIND,WAND SEEDS,SESAME RIDDLE(E),PUZZLE INSIDE,OUTSIDE SHORE,BEACH OZ,WIZARD DEODORIZE,STINK HOW,TO PROGRAM(E),CODE REP,REPUTATION
The puzzle satisfies the series' inbuilt assumption, that each word can be tested for whether it is a Outside Word™ without relying on the other words.
These are not the only examples of Outside Words™; many more exist.
What is the special rule these words conform to?