The opposite of cross-eyed is wall-eyed, but any kind of deviation from both eyeballs pointing straight ahead is called strabismus.
The technical terms for these conditions are esotropia (cross-eyed) and exotropia (wandering eyes, or walleyed). Hypertropia is when one eye wanders up.
About 5 percent of all children have some degree of strabismus, which most of the time can be corrected with surgery.
If you cross your eyes they won’t stay stuck that way?