If you type the word “visceral” into google you can get this response:

visceral

Main Entry:

vis·cer·al

Pronunciation:

ˈvi-sə-rəl, ˈvis-rəl

Function:

adjective

Date:

1575

1 : felt in or as if in the viscera : deep <a visceral conviction>

2 : not intellectual : instinctive, unreasoning <visceral drives>

3 : dealing with crude or elemental emotions : earthy <a visceral novel>

4 : of, relating to, or located on or among the viscera : splanchnic <visceral organs>

— vis·cer·al·ly -rə-lē adverb

However this is referring to the dictionary meaning. Visceral in reference to design it can mean something completely different. My understanding of visceral is the emotional response with in the first 90 seconds. That response could be shock, horror, love, happiness. It’s said that when a person is viewing an artwork or music you have about 15 seconds to impress them. I believe this is in reference to someone’s visceral reaction.

References:
http://www.merriam-webster.com/dictionary/visceral
http://arts.guardian.co.uk/features/story/0,11710,1166468,00.html
http://www.lukew.com/ff/entry.asp?42
http://www.uxmatters.com/MT/archives/000019.php