Definition of fail

• fail to do something; leave something undone; "She failed to notice that her child was no longer in his crib"; "The secretary failed to call the customer and the company lost the account"
• be unsuccessful; "Where do todays public schools fail?"; "The attempt to rescue the hostages failed miserably"
• disappoint, prove undependable to; abandon, forsake; "His sense of smell failed him this time"; "His strength finally failed him"; "His children failed him in the crisis"