A 'reason for action' is the standard term in Anglophone philosophy for a source of normativity of any kind. For example, a desire is the source of normativity in a hypothetical imperative. Others have proposed that categorical imperatives exist, and provide reasons for action apart from desires. Some have proposed that divine commands exist, and are sources of normativity apart from desires. Others have proposed that certain objects or states of affairs can ground normativity intrinsically - i.e. that they have intrinsic value apart from being valued by an agent.

A source of normativity (a reason for action) is anything that grounds/justifies an 'ought' or 'should' statement. Why should I look both ways before crossing the street? Presumably, this 'should' is justified by reference to my desires, which could be gravely thwarted if I do not look both ways before crossing the street. If I strongly desired to be run over by cars, the 'should' statement might no longer be justified. Some people might say I should look both ways anyway, because God's command to always look before crossing a street provides me with reason for action to do that even if it doesn't help fulfill my desires. But I don't believe that proposed reason for action exists.