1. noun /ˈreɪnbəʊ/lang=en
a) A multicoloured arch in the sky, produced by prismatic refraction of light within droplets of rain in the air.
a rainbow of possibilities
Many electoral promises are rainbows, vanishing soon after poll day.
See Also: crossbow
2. adjective /ˈreɪnbəʊ/lang=en
a) Multicoloured.
Similarly, the question of who belongs in such a rainbow alliance isnt set. It can include gay men, lesbians, bisexuals and transgender individuals. It can include people who are questioning which culture they belong to [...]
b) Mellow, laid back, peaceful.
3. verb /ˈreɪnbəʊ/lang=en
To pattern with many colours, like a rainbow.
Wikipedia foundation.