1.an unsteady uneven gait
2.an unintentional but embarrassing blunder;
he recited the whole poem without a single trip
1.walk unsteadily;
The drunk man stumbled about
2.miss a step and fall or nearly fall;
She stumbled over the tree root
3.encounter by chance;
I stumbled across a long-lost cousin last night in a restaurant
4.make an error;
She slipped up and revealed the name