gratuitous
1. [ adjective ] without cause
Examples:

"a gratuitous insult"

Related terms: unmerited
2. [ adjective ] costing nothing
Synonyms: free costless gratis complimentary
Examples:

"complimentary tickets"

Related terms: unpaid
3. [ adjective ] unnecessary and unwarranted
Synonyms: needless uncalled-for
Examples:

"a strikers' tent camp...was burned with needless loss of life"

Related terms: unnecessary
Similar spelling:   gratuitously
  gratuity
  gradation
  gradational