Dictionary Definition :
Definition[1]
:
The three divisions of the 十二因緣 twelve nidānas, q.v.: (a) past, i.e. the first two; (b) present— the next eight; (c) future— the last two.
Source
:
A Dictionary of Chinese Buddhist Terms, William Edward Soothill and Lewis Hodous
Definition[2]
:
(名數)十二因緣涉於過現未三世謂之三節。無明,行之二者為過去。識乃至有之八者,為現在。生,老死之二者為未來。舊俱舍論七曰:「如是緣生法,十二分三節,前後際二二,於中八。」寄歸傳二曰:「不悟緣起三節,從死趣死。」
Source
:
丁福保《佛學大辭典》