It's when we we see (directly or indirectly) that a character's body is completely inside another one.

Related tags

• belly
• vore

Not to be confused with

• after_vore - When the character is completely digested, absorbed or safely released.
• almost_fully_inside - When the character is almost fully inside, still visible from outside.
• partially_inside - When the character is partially in the other one, not completely inside.