Dictionary Definition :
Definition[1]
:
Sixteen "feet", the normal height of a Buddha in his "transformation body" 化 身 nirmāna-kāya; said to be the height of the Buddha when he was on earth.
Source
:
A Dictionary of Chinese Buddhist Terms, William Edward Soothill and Lewis Hodous
Definition[2]
:
丈六===(術語)身長一丈六尺,是通常化身佛之身量也。佛說十二遊經曰:「調達身丈五四寸,佛身長丈六尺,難陀身丈長五四寸,阿難身長丈五三寸,其貴姓舍夷一丈四尺,其餘國皆長丈三尺。」行事鈔下曰:「明了論云:人長八尺,佛則倍之丈六。」業疏四上曰:「佛在人倍,人長八尺,佛則丈六,並依周尺以定律呂也。」觀無量壽經曰:「阿彌陀佛,神通如意,於十方國變現自在。或現大身滿虛空中,或現小身丈六八尺,所現之形皆真金色。」
Source
:
丁福保《佛學大辭典》