Here's a website with the definition.

http://ejje.weblio.jp/content/四級アンモニウム塩基

ライフサイエンス辞書

四級アンモニウム塩基
* よんきゅうあんもにうむえんき
(n*) quaternary ammonium base



四級アンモニウム塩基を英語に訳すと * よんきゅうあんもにうむえんき (n*) quaternary ammonium base.


--------------------------------------------------
Note added at 16 mins (2010-05-06 14:55:37 GMT)
--------------------------------------------------

Here's the English definition of the term:

http://www.answers.com/topic/quaternary-ammonium-base

(′kwät·ən′er·ē ə¦mō·nē·əm ′bās)
(organic chemistry) Ammonium hydroxide (NH4OH) with the ammonium hydrogens replaced by organic radicals, such as (CH3)4NOH.