The term 'Ark Welder' is a job title for someone who works on boats. It is derived from the biblical story of Noah's Ark, where Noah was instructed to build an ark to save himself and his family from the flood. The job involves welding and repairing boats, as well as other related tasks. The crossword solution for this term is 'BOATMAN', which is a seven-letter word that describes someone who works on boats.