What is No Gain in Football?
In Football, 'no gain' refers to an offensive play that didn't lose or gain any yards on the play. If the play were to lose yards, it would be referred to as 'loss of yards', while gaining yards would referred to as 'yards gained'.
No gains always occur during an incomplete pass, barring penalty yards, as the next down in the down cycle will begin with the down and distance to the next 1st down being exactly the same. No gains on rushing plays are very rare, but often occur when the defensive front meets the offensive front at the line of scrimmage and prevents any sort of gain.