caustic - Sarcastic or severely critical, often in a hurtful or biting manner; or able to burn or corrode organic tissue, typically referring to chemicals or substances.

The caustic chemical spilled onto the floor and quickly started to eat away at the floor surface.
shortcut - A simplified way to complete a task, often by bypassing steps in a process; or a path or way that reduces the usual time or distance required to reach a destination.

He surprised the teacher by figuring out a shortcut method of solving the math problem that saved time compared to the method she had taught before.