«وهو بناء البيت على قافيتين يصح المعنى عند الوقوف على كل منهما»
It is to construct a verse with two rhyme endings, the meaning remaining sound when one stops at either.
The device is also called tawshīḥ or dhū al-qāfiyatayn]. A poet supplies an earlier potential ending and then extends the verse to another admissible ending.
The mere presence of two similar-sounding expressions is insufficient. Each stopping point must support coherent meaning and an admissible metrical reading; otherwise the structure does not meet the definition.