It means the last time the user (whose profile you are checking) had accessed WhatsApp. It may not always be right (Android users report problems where they appear online 24x7).
There's no working method available to hide the last seen timestamp on WhatsApp. May be the next WhatsAp update will bring in a feature to do that.
The person either has you blocked, has deleted his account, or does not a profile picture on the Whats app if you can't see a picture.
he was last seen in the underworld
when was magnesium last seen
Jesus was last seen at the Ascension.
She was last seen in Mount Olympus.
Athena was last seen in Rome
he was seen in last in china
Where was billy the kid last seen He was last seen in Marshall I'm a dork Madison
She was last seen at Lae, New Guinea.
He Was Last Seen At A Burning Church.
They've probably blocked you, happened to me today too