The crossword solution for the term CURVE SIGMOID is ESS, which stands for Exponential Sigmoid Function. This is a type of mathematical function that is used to describe non-linear relationships between two variables. It is often used in machine learning algorithms and neural networks to model complex data. The sigmoid curve is also known as an S-shaped curve because of its shape. It is used to map input values to output values in a range from 0 to 1.