Sime specific way of perceiving their environment. Being able to read the life energy of other living beings through their lateral tentacles. This is how simes hunt Gen. Sime can zlin only when duoconscious or hyperconscious. When hypoconscious, the sime can only see, hear, taste, smell, or touch, using the senses the sime has in common with Gens. (From House of Zeor Ch 3) 'Simes read emotions as clearly as words.'
(From Considerations of the "SEC" prefix, suffix, infix, particle in Simelan. source: http://www.simegen.com/sgfandom/rimonslibrary/zf/simemain.html)
Think of a thin rubber sheet with sticks poking up here and there stretching the sheet into peaks - and something else here and there pulling the sheet down into peaks that go downward. That's how Simes perceive their local surroundings when duo or hyperconscious.
The same scene will appear very differently to a sime when zlinning than a Gen who cannot.