Wiktionary
n. (context construction English) The process of renewing mortar joints in masonry
Wikipedia
Repointing is the process of renewing the 'pointing, which is the external part of mortar joints, in masonry construction. Over time, weathering and decay cause voids in the joints between masonry units, usually in bricks, allowing the undesirable entrance of water. Water entering through these voids can cause significant damage through frost weathering and from salt dissolution and deposition. Repointing is also called pointing, or pointing up, although these terms more properly refer to the finishing step in new construction.
Usage examples of "repointing".
Satisfied with the repointing, he scraped his trowel on the edge of the bucket.
More important matters were afoot than repointing stonework or painting.