This is in the spirit of the What is a Word/Phrase™ series started by JLee with a special brand of Phrase™ and Word™ puzzles.
If a word conforms to a special rule, I call it a Horsethorn Word™. Use the following examples below to find the rule.
And if you want to analyze, here is a CSV version:
Horsethorn Words™, Not Horsethorn Words™ LAKE, OCEAN PINHOLE, CAMERA HUMANLIKE, ANIMALISTIC APHELION, PERIHELION LUPINE, FLOWER UPLINK, DOWNLINK HAIKU, RHYME MOULIN, MAUDLIN WEAPON, GUN LOW, HIGH HOWL, YELL WHALE, SHARK PILLOW, COTTON WOMAN, LADY OPIUM, POPPY LEMON, ORANGE AMPOULE, NEEDLE