Open the wish on Wishpicks and tap Cancel reservation, or go to Wishes → For others, tap ⋮ next to the gift and choose Cancel reservation.

From the wish, on a phone or a computer:

From Wishes → For others:

The window warns: "Once the reservation is cancelled, other people will see [wish] as available again." Afterwards you'll see "You cancelled your reservation for [wish]", and the gift drops out of your For others.

The card has a shortcut too: on a computer, hover over it and click Cancel reservation; on a phone, it's the first option in the card's ⋯ menu.

Yes. If the Reserved window is still open, tap Cancel reservation there and it's undone straight away, with no confirm step. Closed it already? Cancel it with the steps above.

Changed your mind again? Reserve it again, as long as nobody else has taken it in the meantime. A note you left goes with the cancelled reservation, so write a new one if you want.

Cancelling doesn't undo a purchase. If you've already bought the gift, any return goes through the shop: see "Does Wishpicks deliver the gift?".

Either the owner has marked the wish as received, or you reserved without an account in another browser or on another device.

If the wish says "[name] already has this." and has no cancel button, cancel from Wishes → For others instead.

If you reserved in another browser, "Where can I see the gifts I've reserved?" explains what to do.