In GTD parlance defer doesn't require a calendar appointment, it just means 'don't do right now'. Basically if a task takes more than 2 minutes to do but you intend to do it at some point, then it should not interrupt processing, but should be moved from an inbox to a 'trusted system' for organizing and tracking tasks.

Snoozing works ok, but strict GTD tries to build a discipline of not having items re-appear in the inbox. If it's moved to a list of things to handle, then it can be ignored or placed at a lower priority on that list.