It is an adjective.
Meaning : considering the whole rather than individual parts.It is used to emphasize the importance of the whole rather than individual parts.
Root of the word: hol = whole
Synonyms: complete, entire
Antonyms : narrow
holistically - adverb
1)A holistic approach to transport may be the solution to most of our commutation problems.
2)A holistic medicine will surely cure the disease.
3)Always look at things holistically.