indispensable• For mountain-climbing a really good sleeping-bag is indispensable.• If you're planning on going sightseeing around the old city, a guide is indispensable.• Police dogs have provedindispensable in the war on drugs.• She soon became an indispensablemember of staff.• A knowledge of classicalmusic is indispensable to anyone who wants to apply for this job.• The book will be indispensable to anyone who wishes to learn more about the BritishRoyal Family.