Dictionary.net

• a program of space flights undertaken by US to land a man on the moon; "the first lunar landing was achieved by the Apollo program on July 20, 1969"

2006 - WordNet 3.0
By Princeton University

• a program of space flights undertaken by US to land a man on the moon; "the first lunar landing was achieved by the Apollo program on July 20, 1969"

2011 - English Dictionary Database
By DataStellar Co., Ltd