Immersion

noun

1. The act of immersing or the condition of being immersed.
2. An immersion heater.
3. A smooth map whose differential is everywhere injective, related to the mathematical concept of an embedding.
4. The disappearance of a celestial body, by passing either behind another, as in the occultation of a star, or into its shadow, as in the eclipse of a satellite.
5. A form of foreign-language teaching where the language is used intensively to teach other subjects to a student.