This trophy is earned by learning 150 alien words. They don't have to be from the same species. You can learn alien words by:
1) Conversing with any that you meet and requesting words when given the option
2) Interacting with monoliths on planets you visit (You can use the beacons that you activate with the bypass chip to find them if you don't stumble across them on your own)
3) Interacting with knowledge stones scattered throughout the planets you visit. Use your visor scanner and look for purple icons with what appear to be one-eyed cylinders.
4) (Thanks to MH_The_Rockstar for the tip) Visiting an Atlas anomaly can net you several words at once.