The usage of 地道

Literally 地道 means tunnel, subway, or underpass. There was a classic movie called 地道战 (the War in the Tunnel) , which was about the story of Chinese soldiers and farmers dug tunnels underground to fight the Japanese invaders in the 1940s. 
But in our daily conversation, 地道 has quite a few different interesting usages. Let's see some examples:

她的普通话说得真地道。
She speaks perfect mandarin.
他干的活儿真地道。
His work is really well-done.
In above sentences, 地道 means perfect, or skill up to standard. 

那家中餐馆的饭菜很地道。
The food in that Chinese restaurant is really authentic. 
In this sentence, 地道 means authentic.

这是地道的龙井茶。
This is genuine Longjing tea.
Here, 地道 means from the place well-known for a certain product;

那人很不地道。
That person is not an honest one. He cheated. 
In this sentence, 地道 means honest, obey the common moral rules.