Can we get Item definition displayed in tooltip?
 

How do we get the item description which is displayed in tooltip?

e.g. for Lockpicks it's :
"Used to open many chest and doors.
Expanded upon use."

Did you check the API Documentation Pxx.txt files for something like GetItem* Info or GetItemLink* Info, similar. Maybe there is some function returning the text as String parameter.

Yes I checked there is :

GetQuestItemTooltipText(*integer* _questItemId_)
** _Returns:_ *string* _tooltipText_

but I couldn't find one for a regular item.

ah I found it it's :
GetItemLinkFlavorText(itemLink) :)

Yeah, this one was it! Sorry, I initially thought it was

* GetItemInfo(*[Bag|#Bag]* _bagId_, *integer* _slotIndex_)
** _Returns:_ *textureName* _icon_, *integer* _stack_, *integer* _sellPrice_, *bool* _meetsUsageRequirement_, *bool* _locked_, *[EquipType|#EquipType]* _equipType_, *integer* _itemStyleId_, *[ItemQuality|#ItemQuality]* _functionalQuality_, *[ItemDisplayQuality|#ItemDisplayQuality]* _displayQuality_