[They sat together upon their knees], (S, K,) in contending or disputing; verbal noun مُجَاثَاةٌ and جِثَاءٌ, which are [properly inf. ns. of 3, but are] thus used as inf. ns. of a verb to which they do not conform. (TA.)
2.
التَّجَاثِى فِى إِشَالَةِ الحَجَرِ is like التَّجَاذِ ى [The vying, one with another, in lifting the stone, for trial of strength]. (TA.)