Help:Advanced Wiktionary skills
Amazing things are possible using CirrusSearch. See mw:Help:CirrusSearch.
Examples include fuzzy text searches and searches for entries with templates, entries with regular expressions in the wikitext, entries in categories and in subcategories of other categories, and combinations of these and others.
Search can be used to create ad-hoc lists to for making changes to entries, to clean up errors or to provide missing content, etc.
Searching inside categories
PetScan is a handy tool to find entries in more than one category, or in one category and not another.