introduce (a liquid, especially a drug or vaccine) into the body with a syringe

the doctor injected a painkilling drug

introduce (something) under pressure into a passage, cavity, or solid material

inject the foam and allow it to expand

introduce (a new or different element) into something

she tried to inject scorn into her tone

place (a spacecraft or other object) into an orbit or trajectory

many meteoroids are injected into hyperbolic orbits