Warp Blast
From Exterminatus Manual
++Weapons++
The Tyranid Zoanthrope is a very specialized breed, it appears to be a genetic combination of both Tyranid and Eldar DNA that results in a creature with powerful psychic abilities, including it's primary attack the Warp Blast.
Firing Modes
The Zoanthroapes primary attack is to rapidly launch explosive bolts of psychic warp energy, drawn from the collective hive mind. It's secondary attack draws from the same reserve, but uses all the energy the Zoanthrope can muster in a single large burst (sometimes referd to as the "Afro Cannon", due to the spherical rupture of warp space it causes).
Tactics
Psychic attacks are not blocked by armor and so are equally effective against Terminators and regular marines. A Warp Blast (2ndary attack) cause massive damage and can kill with a single hit, however they do leave the Zoanthrope vulnerable until they can draw more energy.