lehr

This term is a highly specialized technical noun used almost exclusively within the glass manufacturing industry. It describes a specific type of annealing oven designed to cool glass at a controlled rate, preventing the structural failure that occurs when glass is cooled too rapidly.

Because it is a piece of industrial equipment, it is used in a literal, physical sense. It does not have metaphorical extensions or common usage in general conversation, appearing primarily in engineering manuals, industrial patents, and glass-blowing textbooks.