What does 7 or 8-slotted hero in DoTA 2 mean?

I see in some forums they mention 7-slotted <name of hero here> that they use in some match. I also see 8-slotted and I think I even saw the term 12-slotted thrown in some discussion. What does that mean? I know the maximum number of items you can carry is 6 so what are they talking about?

Solution 1:

In some really long matches (say more than an hour) you will have a lot of extra gold left over even after saving for buyback. Some ways you can be more than 6 slotted are:

• Suppose your hero works well with a refresher orb. Then after you get your 7th item you could put the refresher in your stash(back in base) and use when its off cooldown (which is 180 secs) as this optimizes your inventory. This can be done with any other item as well.
• You can buy an item called moonshard (buy two hyperstone from secret shop) which passively gives +120 attack speed (also increased night vision). However, this item can be consumed to get a permanent +60 attack speed(no increased night vision though). Well obviously consuming a moonshard while you still have free inventory slots is a big mistake you can consume it keep that one additional item. Plus, the Attack Speed from multiple moonshard stack..
• Alchemist's Aghanim's Scepter upgrade is that he can gift it to another ally.
  More about that here.
  Alchemist is an hero which if played well can easily get 6-slotted in 25-30 mins(because of his passive Greevil's Gold). So after that an Alchemist will spend his surplus gold on either Aghanims for his teammates or buy and consume moonshards.
• Lone Druid has an ability which summons a spirit bear and this bear can carry items too. This gives Lone Druid 12 slots and a fully farmed lone druid is effectively 12 slotted. More about Lone Druid. (Thanks to DanmakuGrazer for this point).

Edit 1: As pointed out by Mandeep, Multiple Moonshard do not stack and you can consume only one. But in the case of Lone Druid, his Spirit Bear can also consume a moonshard.

Edit 2: Divine Rapier is an item which gives +330 damage and drops on death. So rapier is a high-risk-high-reward item and losing one to the enemy's carry may just result in a loss for you. To workaround this problem, heroes like Ember Spirit, Medusa and Gyrocopter will make extra rapiers which they will store in their inventory so that even if they do drop their rapier they'll still have one when they respawn. (Thanks to Fatalize for this point.)