Eater 3 is a large symmetric eater that was found by David Buckingham on June 22, 1977 and has a very different eating action from eater 1 and eater 2; however, it shares with those two eaters the ability to eat gliders. The loaf can take bites out things, being flipped over in the process. The rest of the object simply flips it back again. Two copies of the eater 3 can share a loaf, forming the period 8 oscillator shown below.
The eater 3 can be reduced in area by using snakes rather than tubs in the casing; this property is used to compact the rectifier.
On July 2, 2016, Mark Niemiec found an 18-glider synthesis based on a reaction found by Bullet51, for an eater 3 variant using buns as stabilizers. Before this the cheapest known construction recipe for any eater 3 variant needed 72 gliders. In April 2020 GUYTU6J reduced this to 16 gliders.