Merriam-Webster Collegiate Dictionary - stumble

 I. verb  (~d; stumbling)  Etymology: Middle English, probably of Scandinavian origin; akin to Norwegian dialect stumle to ~  Date: 14th century  intransitive verb  1.  a. to fall into sin or waywardness  b. to make an error ; blunder  c. to come to an obstacle to belief  2. to trip in walking or running  3.  a. to walk unsteadily or clumsily  b. to speak or act in a hesitant or faltering manner  4.  a. to come unexpectedly or by chance ~ onto the truth  b. to fall or move carelessly  transitive verb  1. to cause to ~ ; trip  2. bewilder, confound  • ~r noun  • stumblingly adverb  II. noun  Date: 1547 an act or instance of stumbling