Ambisinistrous

ambisinistrous \ˌam-bi-ˈsi-nəs-trəs\ adjective: lacking facility in both hands

Etymology: Latin ambi- both + sinister on the left

I don’t need to point out that ambisinistrous (literally “having two left hands”) is antonymous with ambidextrous (“having two right hands”). Thanks to reader Vicki Peter for suggesting this entry word.