Welding is a process of joining two or more materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, forming a permanent bond. Welding with a blowtorch is a common method used to join metal components, as it is relatively inexpensive and easy to use. The term for this process is 'WELD, ' which is a four-letter word that can be used to complete the crossword puzzle.