Of course it is
Strictly speaking, most oral contraceptives are "abortion pills" as well, since they work by preventing a fertilized egg from attaching to the uterus wall, the fertilized egg will therefore evacuate and die. Just like an abortion...just really early.
Strictly speaking, that's not really true. While the precise mechanism is a matter of some debate, the available evidence indicates that all hormonal contraceptives, including emergency contraception, work by preventing ovulation, not fertilization or implantation. If all you're doing is preventing ovulation, you're certainly not causing an abortion, not by anyone's definition.