The word honestly in its most basic usage means in an honest and truthful way. You might say, “I asked my little brother if he ate the last cookie and he replied honestly, saying that he did.”

The word honestly can also express frustration or emphasis, like when someone says, “Honestly, I have no idea what you're talking about!” In this case, they're stressing that they're being completely truthful or that they're genuinely confused or exasperated.