Ambilevous

Again, Some are Ἀμφαριστεροὶ as Galen hath expreſſed : that is, Ambilevous or left-handed on both ſides; ſuch as with agility and vigour have not the uſe of either : who are not gymnaſtically compoſed : nor actively uſe thoſe parts. Now in theſe there is no right hand : of this conſtitution are many women, and ſome men, who though they accuſtome themſelves unto either hand, do dexterouſly make uſe of neither.

Source: wiktionary

Whereas the ambidextrous person is regarded as one who is capable of using both hands with equal dexterity, there are others, referred to as ambilevous, who use both hands equally awkwardly.

Source: wiktionary

The ambilevous (the opposite of ambidextrous) child is unable to use either hand more skillfully than the other, but is equally awkward in the use of each.

Source: wiktionary

I as a right-handed person do not have the option of becoming genuinely ambidextrous, literally one with ‘two right hands’. And I surely must guard against sinking into one is who is doubly left-handed, or ambilevous. (We may notice the prejudice uncovered by etymology.) But I can, by will and practice, lessen the native inferiority of my weaker side.

Source: wiktionary