Assem AlKhallouf Apr 10, 2017:

In MSA and Sudanese Arabic. I have read Wikipedia article before answering, and it is not clear.
شمة is from يشمّ (smell)
سعوط is نشوق (snuff)
While تمباك:
1- In Modern Standard Arabic and in Egypt: (hookah tobacco)
تُمْباك : تبغ يدخن في النارجيلة .
http://www.almaany.com/ar/dict/ar-ar/تمباك/
ويغسل التمباك عدة مرات بالماء، ثم يقطع ويوضع في حجر الشبك وهو رطب، ويوضع عليه جمرتان أو ثلاث
http://www.almasalik.com/locationPassage.do?locationId=29854...
Nargile Tobacco
http://dictionary.torjoman.com/search/1-2/تنباك

تُنْباك ( اسم ): تَبَغٌ فارِسِي tobacco - a solanaceous plant with narcotic leaves used for smoking.
http://www.almaany.com/ar/dict/ar-en/تنباك/

2- In Sudan: (I think it is better to transliterate it as Tunbak)
ويتم تعاطي التمباك الذي يطلق عليه أيضا “الصعوط أو العماري” بتجهيز قطعة دائرية صغيرة منه يطلق عليها “سفة” وتوضع ما بين الفك والشفاه
http://www.almrsal.com/post/326368

*In Arabic, تمباك and تنباك are like "Improper" from "Inproper".

Susan McMillan (asker) Apr 10, 2017:

تمباك وشمة وسعوط؟ I received some very helpful information in an from a kind colleague:

"This stuff is almost the same material some sniff it
(fermented tobacco with some sorts of local spices) but
instead of inhaling it people in Sudan and southern of Egypt put some of it between their lips and teeth. They call it سَعُوط as well. If you know an exact name of that stuff, please let me know it."

That also conforms with the first line of this Wikipedia entry: https://ar.wikipedia.org/wiki/شمة

Chewing or dipping tobacco is very different from hookah tobacco, so I'm still confused about which is correct.