"Goal deficit" refers to a situation where a team or individual has scored fewer goals than their opponent. It means that they are behind or losing in terms of goals scored. Full definition
It is a strong Arsenal side but we will have to be at our best to overcome a two goal deficit against a side that does not seem to concede goals. (justarsenal.com)
His teammates were able to overcome their one goal deficit from the first leg to advance 3 - 2 on aggregate. (giusepperossi.net)
This is apparently the first time that we make up a 2 - goal deficit away from home since 2011. (justarsenal.com)