The most frequent meaning is of a sexual nature, especially if the dreamers are young. It also symbolizes wisdom and healing power. Seeing a sleeping snake indicates that our instinctual forces are asleep. If it wakes up and wriggles without causing fear, it reveals desires of a spiritual evolution. Dreaming of snakeskin or seeing change indicates that a profound evolutionary change is coming. If poisonous snakes appear, it indicates fear to be in embarrassing situations.
Dream dictionary: boa cobra and snake dream meanings
(see cobra, boa, viper, asp).