1.Definition: deprived of life; no longer living

"A lifeless body"

Related Adjective(s):exanimate

2.Definition: destitute or having been emptied of life or living beings

"After the dance the littered and lifeless ballroom echoed hollowly"

3.Definition: lacking animation or excitement or activity

"It was a lifeless party until she arrived"

4.Definition: not having the capacity to support life

"A lifeless planet"