For anyone else that might be curios, the definition of a planet you will often see quoted online applies to bodies in our Solar System. It comes from the International Astronomical Union in 2006. This is the famous definition that dropped Pluto as a planet. While the criteria are widely quoted, that actual resolution isn't. The resolution:

The IAU...resolves that planets and other bodies, except satellites, in the Solar System be defined into three distinct categories in the following way:

(1) A planet [1] is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape [2], (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

(3) All other objects [3], except satellites, orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".

The definition here only applies to bodies in the Solar System.

Still a bad definition IMO. According to the definition if a catastrophic event were to occur that cluttered the neighborhood of a planet it would cease to be a planet until it was cleaned up. The definition of a planet should be based in the physical attributes of the celestial body itself, not in its role or relationship with other bodies. I'm a bit of an extremist on this front. Even our Moon would be a planet in my opinion. Seems silly when you think about our barren moon but there are for sure habitable moons out there. I can't imagine asking an alien "What planet are you from?" and them responding "erm, actually we are from a moon/planetary satellite".

Right? It's biology when you study enzymes in vitro, but as soon as you put a membrane around them then it's ... something else?

Bizarre argument.