What does “mā lā yalzam” mean in this ornament?

Qalb, Tashrīʿ and Luzūm Mā Lā Yalzam: Completing the Verbal Ornaments

• A condition indispensable for meaning
• A mandatory letter in every valid rhyme
• An additional self-imposed condition beyond rhyme or sajʿ
• Abandoning verse metre