Participants were randomly assigned to then either judge the veracity of each headline (accuracy condition) or indicate whether they would consider sharing each headline online (sharing condition)
So they use "accuracy" as an alias for "veracity". But they don't really need to define it, because the study is about what the participants think is accurate, not the researchers.
EDIT: Now that I've made it down to the methods section, I see that the wording they actually used was "We are interested in whether you think these headlines describe an event that actually happened in an accurate and unbiased way." So, their measurements refer to whatever the participants interpreted that question to mean.
Participants were randomly assigned to then either judge the veracity of each headline (accuracy condition) or indicate whether they would consider sharing each headline online (sharing condition)
So they use "accuracy" as an alias for "veracity". But they don't really need to define it, because the study is about what the participants think is accurate, not the researchers.
EDIT: Now that I've made it down to the methods section, I see that the wording they actually used was "We are interested in whether you think these headlines describe an event that actually happened in an accurate and unbiased way." So, their measurements refer to whatever the participants interpreted that question to mean.