Protists

noun a single-celled microscopic organism that has no definite shape and moves by constantly changing its form

• The scientist observed the movement of the single-celled organism known as an amoeba under the microscope.
• I heard that an amoeba can change its shape to fit into tight spaces.
• That guy is like an amoeba, always changing his mind and adapting to different situations.
• Her ideas seemed to flow and change shape like an ever-moving amoeba.

noun a genus of freshwater protozoans known for their spherical shape and long, radiating pseudopods

• Actinophrys is a genus of freshwater protozoa known for their distinctive appearance and feeding behavior.
• Have you ever seen an actinophrys under a microscope? They look so cool!
• That actinophrys is like a tiny alien living in the water.
• Her dance moves were as mesmerizing as the tentacles of an actinophrys.