Althought there are many expressions denoting Nibbana, even and especially by the Buddha: No, is't not possible to describe, just or simply not in the sphere of "All", senses and their faculties, since it lies beyond.
"Monks, I will teach you the All. Listen & pay close attention. I will speak."
"As you say, lord," the monks responded.
The Blessed One said, "What is the All? Simply the eye & forms, ear & sounds, nose & aromas, tongue & flavors, body & tactile sensations, intellect & ideas. This, monks, is called the All.  Anyone who would say, 'Repudiating this All, I will describe another,' if questioned on what exactly might be the grounds for his statement, would be unable to explain, and furthermore, would be put to grief. Why? Because it lies beyond range."
This work, which might give a notion, might be a useful inspiration to "see and realize for oneself":
Mind Like Fire Unbound: An Image in the Early Buddhist Discourses (Fourth Edition), by Thanissaro Bhikkhu (Geoffrey DeGraff) (1999; 4pp./11KB)
Early Buddhism borrowed two of its central terms from the workings of fire. Upadana, or clinging, originally referred to the fuel that kept fire burning; nibbana, the name of the goal, to a fire's going out. This is the first book to examine these terms from the perspective of how the early Buddhists themselves viewed fire — what they saw happening as a fire burned, and what happened to the fire when it went out — to show what light this perspective throws on Buddhist doctrine in general, and the practice of meditation in particular. With extensive quotations from the Pali canon, newly translated, this is also a useful sourcebook for anyone who wants to encounter Buddhist teachings in their earliest known context.
Nibbana is displayed in the third Noble Truth, which might be the most proper way to describe it, yet it lies beyond the sphere of imagination, because there is nothing compareable in the sphere of the six senses:
"Now from the remainderless fading and cessation of that very ignorance comes the cessation of fabrications. From the cessation of fabrications comes the cessation of consciousness. From the cessation of consciousness comes the cessation of name-and-form. From the cessation of name-and-form comes the cessation of the six sense media. From the cessation of the six sense media comes the cessation of contact. From the cessation of contact comes the cessation of feeling. From the cessation of feeling comes the cessation of craving. From the cessation of craving comes the cessation of clinging/sustenance. From the cessation of clinging/sustenance comes the cessation of becoming. From the cessation of becoming comes the cessation of birth. From the cessation of birth, then old age and death, sorrow, lamentation, pain, distress, and despair all cease. Such is the cessation of this entire mass of stress and suffering.
read more about the third Noble Truth & Nibbana
[Note: This is a gift of Dhamma and not meant for any commerzial purpose or other low wordily gains by trade and exchange.]