A "strictly increasing function" is a mathematical term used to describe a function where the output value of the function increases as the input value increases. Synonyms for this term include "monotonic increasing function," "non-decreasing function," and "positive slope function." These synonyms describe the same concept where the function maintains a certain direction and does not decrease at any point. Additionally, the terms "order-preserving function" and "rising function" can also be used to describe a strictly increasing function. The use of such synonyms helps to clarify the concept of a mathematical function that has a predictable direction and movement.