What is the term for moving perpendicular to a ranged enemy with physics-based projectiles?

Lateral movement has many terms which are used in games: Strafing, Side-stepping, crab walking.

Lateral movement with intent to avoid slow moving projectiles... is pretty specific and doesn't really have commonly used gaming terms. Here are some scenarios and common terms used to describe them.

• The projectile is headed for your current position. If you move out of the projectile path, terms that apply are "avoid" or "dodge".
• The projectile has been launched with your current lateral movement in mind - aka the shooter used "leading". If you change your lateral movement, by stopping or reversing it, you will not enter the path of the projectile. A term that applies is "faking out". An advanced form of this is to make small lateral motions in place. The idea is to continuously generate lead targets in positions you never occupy, or generate lead targets which are behind obstacles.
• The projectile is launched from a gun which has a specific turn rate (such as is found in eve-online). If your lateral motion outpaces the gun's turn rate, then the gun cannot "track" you. In eve-online, specifically, this movement is called "transverse" movement.

My favorite word for this would be Serpentine:

a : winding or turning one way and another

I have heard this used specifically for dodging incoming fire (regardless if you're approaching or running away from said source of incoming fire).

Here's a good example.

You answered your own question. Its dodging. Strafing is not strictly applicable as it applies to shooting at (or back at) a target - its original usage was to describe an attack run of a aircraft.

Jinking is a word that's sometimes specifically used to refer to dodging incoming fire.

http://www.thefreedictionary.com/jinking