snot: nasal mucus
mucus: protective secretion of the mucus membranes; in the gut it lubricates the passage of food and protects the epithelial cells; in the nose and throat and lungs it can make it difficult for bacteria to penetrate the body through the epithelium
seesaw: a plaything consisting of a board balanced on a fulcrum; the board is ridden up and down by children at either end