Drily
/ˈdraɪli/
Definition 1 of 1
Pro Tip 1/3Subtle Humor
Used to describe comments that are witty but not obviously funny, often missed by others. 
He drily observed that the so-called 'all-day' event ended at noon.
Pro Tip 2/3Emotionless Delivery
The speaker's voice is often monotone or unenthusiastic, which is part of the dry humor. 
When she lost the game, she drily said, 'Well, that was exciting,' with a blank expression.
Pro Tip 3/3Understated Reaction
A drily delivered line might understate the actual situation, providing comedic effect through contrast. 
As the chaos ensued, he drily remarked, 'We've had better days.'