SIRAATUN- Lexicography:
Siraat: Way, path. (Wortabet)
Path to heaven. (J.G.Hava)
Straight and right path. (Vocabulary of the Holy Quran)
Easy Way.
It is considered to have been taken from "Siraatun with Siin" (letter `siin') which means swallowing (food), and is used as a similitude as if to swallow the way in the journey. (Lughatul Quran, Muhammad Abdur-Rashid Nomani and Arabic-English Dictionary by J.G.Hava)
A way, and specially an open way. (John Penrice)

Siraat: "A road" . The word occurs in the Quran thirty eight times , in nearly all of which it is used for the 'Siraat-al-Mustaqiim' or the 'right way' of religion" (Page 595, A Dictionary of Islam, Thomas Patrick Hughes)
Road, the bridge of hell, long sword. (F.Steingass)
"According to which (Zoroastrian system) the spirits of the departed, both good and bad, proceed along an appointed path to the `bridge of the gatherer' (chinvat peretu). This was a narrow road conducting to heaven or Paradise, over which the souls of the pious alone could pass, while the wicked fell into the gulf below. (Rawlinson's Seventh Oriental Monarchy, p.636).

"The Jews , also believed in the bridge of hell, which is no broader than a thread, over which idolaters must pass. (Midrash, Yalkut, Reubeni, sect. Gehinnom)" (A Dictionary of Islam, Thomas Patrick Hughes).

For usage and derivatives of the root word, in the Quran, see pages 516-517 (for Siraat) and 699-708 (for Qaam), Al-Muajamul Mufaharas, Muhammad Fawad Abdul Baqi.