When you receive so much anal sex, that your whole ass gains a complexion of a beautiful tan. But this is not from the sun, but rather a mix of shit, blood, cum and lube. This is usually applied to gay men, and is complimentary.
A bed/booth you lay/stand in. It has ultraviolet bulbs that emit UV very much similar to the sun. It will give you a tan very much like the sun does. There is a possibility skin cancer can be acquired from using one of these devices.
Damn she's tan, she must be using the tanningbed again
Tanning injections refer to the injection of one of the melanotan peptides (melanotan-1 and melanotan II) to develop pigmentation in one's skin thus allowing individuals who ordinarily cannot tan or have difficulty doing so (fitzpatrick skin type I and type II, ie: redheads and gingers) to be able to do so. See: Melanotan.org
United Kingdom Jordan's (Katie Price) boyfriend was amazingly tanned from having used tanning injections.