Wordnet 3.0
ADVERB (1)
1. 
 in a lengthy or prolix manner; 
- Example: "the argument went on lengthily"- Example: "she talked at length about the problem"[syn: lengthily, at length]
The Collaborative International Dictionary of English v.0.48:
Lengthily \Length"i*ly\ (-[i^]*l[y^]), adv.
   In a lengthy manner; at great length or extent.
   [1913 Webster]
WordNet (r) 3.0 (2006):
lengthily
    adv 1: in a lengthy or prolix manner; "the argument went on
           lengthily"; "she talked at length about the problem"
           [syn: lengthily, at length]