Unbid, Unbidden, a.
1. Not bidden; not commanded. Thorns also and thistles it shall bring thee forth Unbid; and thou shalt eat the herb of the field. Milton.
2. Uninvited; as, unbidden guests. Shak.
3. Being without a prayer. [Obs.] Spenser.
Shades of meaning
Fernald has no entry of its own for unbidden; he lists it under spontaneous.
Where he writes about it:
We speak of spontaneous generation, spontaneous combustion, spontaneous sympathy, an involuntary start, an unbidden tear, voluntary agreement, willing submission. — from spontaneous
Antonyms
none given