A verb meaning to boil or cook, and by extension to ripen or bring to maturity. Used both literally (cooking food) and figuratively (God ripening judgment or bringing plans to fruition). The famous prohibition 'thou shalt not seethe a kid in his mother's milk' (Exodus 23:19) uses this root.
The command not to bashal a kid in its mother's milk (repeated three times: Exod 23:19, 34:26, Deut 14:21) became the foundation for Jewish dietary laws separating meat and dairy. But the deeper theological principle is about perverting the natural order: milk is meant to sustain life, not become the instrument of death. The act mocks the nurturing purpose of creation. This connects to a broader biblical theme: God's gifts must be used according to their design. When life-giving things are twisted into instruments of destruction, it grieves the Creator.