length‧y comparative lengthier, superlative lengthiest [usually before noun]
1continuing for a long time, often too long [≠ brief]:
A lengthy period of training is required.
An accident is causing some lengthy delays.
2a speech, piece of writing etc that is lengthy is long and often contains too many details:
a lengthy report
WORD FOCUS: long WORD FOCUS: long continuing for a long time:lengthy continuing for much too long:interminable, marathon, endless, long-winded, long-drawn-out, protracted continuing for a long time and not changing:permanent, lasting, lifelong when feelings last for a long time:lingering, abiding, enduring, lasting ➔ See alsolong
Definition from the Longman Dictionary of Contemporary English Advanced Learner's Dictionary.