Oat hay refers to a type of forage that is frequently used as animal feed. However, there are several other names for this type of hay that may be used interchangeably depending on the region or context. One common synonym is oat straw, which refers to the dry, stripped stalks of the oat plant that are used as fodder. Another synonym is oat chaff, which refers to the husks and other plant debris that are left over after the oats have been threshed. Additionally, some people use the term oat grass to refer to the young, tender shoots of the oat plant when they are still green and suitable for grazing.