Use 'dumbly' when someone is too shocked to speak. After hearing the news, she nodded dumbly, words failing her.
Pro Tip 2/3
Speechless Confusion
'Dumbly' implies a temporary loss of words, often from confusion. The puzzle was so complex that he sat, staring at the pieces dumbly.
Pro Tip 3/3
Emotional Overwhelm
It's appropriate to use 'dumbly' when emotions overpower the ability to speak. Overcome with grief, he could only watch dumbly as others offered condolences.