The term that describes the multicellular haploid form of a protist that shows alternation of generations is gametophyte.

Here's why:

* Alternation of generations: This is a life cycle characteristic of many plants and some algae (protists) where a multicellular haploid generation (gametophyte) alternates with a multicellular diploid generation (sporophyte).

* Gametophyte: The gametophyte is the haploid (n) generation that produces gametes (sperm and egg) through mitosis. These gametes fuse to form a diploid zygote, which develops into the sporophyte.

Example: In some algae, the gametophyte stage is the dominant phase, while in others, the sporophyte stage is more prominent.

Let me know if you'd like more details about the alternation of generations!