To vouchsafe means to grant or give something in a gracious or condescending way, as if you're doing someone a special favor by allowing them to have it. The word carries a sense that the giver has power or authority and is choosing, perhaps generously, to share something they didn't have to share.

You might read in an old story that a king vouchsafed his approval for a plan, meaning he granted his official permission. Or a haughty character might vouchsafe a reply to someone they consider beneath them, meaning they deigned to answer at all.

The word often appears in older literature and formal writing. When someone vouchsafes information, they're revealing something they could have kept secret. If a mysterious stranger vouchsafes an explanation for strange events, they're choosing to share knowledge they could have withheld.

Today, vouchsafe sometimes carries a slightly ironic or critical tone. If you say someone “vouchsafed a response,” you might be suggesting they acted superior or overly formal when a simple answer would have done. The word reminds us that how we give something can matter as much as what we give.