0 not having the standard of living conditions, education, etc. that most people have: --
A new educational programme has been set up for economically disadvantaged children.
1 people who do not have good living conditions, a good standard of education, etc., considered as a group: --
2 (of people) not having the benefits, such as enough money and a healthy social situation, that others have, and therefore having less opportunity to be successful: --
Head Start is an educational program for disadvantaged preschool children.