xū wú piāo miǎo
illusory; imaginary; fanciful
虚
xū
emptiness
无
wú
not to have
缥
piāo
used in 縹渺|缥渺[piao1 miao3]
缈
miǎo
used in 縹緲|缥缈[piao1 miao3]