A "selfless act" means doing something to help or benefit others without expecting anything in return, putting their needs before your own. Full definition
It is truly one of the most selfless acts of love that you can do for your family. (quotacy.com)
But the choice to frame the film in inspirational terms is problematic too, as some of the most selfless acts in the 1996 disaster were arguably punished. (sfgate.com)
We have so far been buoyed by selfless acts of heroism, shaken by the most effective sound effects possibly ever twinned to celluloid and been willfully seduced by a brilliant portrayal of Searle (Cliff Curtis), the Ships slowly unraveling and comically absorbing psychological officer. (mutantreviewers.wordpress.com)