Definition
To act grumpily means behaving in a bad-tempered and sulky manner. It suggests a temporary state of displeasure, often accompanied by complaining or irritability. Someone who replies grumpily is likely to use a surly tone or make negative remarks. It's similar to being in a foul mood and letting it show. Grumpily implies a passing phase of discontent, rather than a permanent personality trait. Think of Eeyore from Winnie the Pooh – he's often grumpy.