Antigravity

3 clues
Sci-fi concept
Like some sci-fi boots
Ideal spacecraft-propulsion method
Similar answers:
Absolutegravity
Antarcticalaskantigua
Antigen
Antigenic
Antigens
Antigenxers
Antigerman
Antiglare
Antigone
Antigravity
Antigua
Antiguan
Antiguans
Antigun
Antiquegravity
Asiantigers
Cantigny
Captaingravity
Centerofgravity
Centreofgravity