Ishmām is a silent rounding of the lips toward the shape of ḍammah after making the final letter still; the vowel is not sounded.
This stopping option pertains to an eligible original ḍammah, not to final kasrah or fatḥah. It is chiefly observable visually rather than as an audible vowel.
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Ishmām: a silent lip gesture
Rules of Waqf — Correct Stopping, Resumption, Rawm, Ishmām and Qurʾānic Orthography
Ishmām is a silent rounding of the lips toward the shape of ḍammah after making the final letter still; the vowel is not sounded.
This stopping option pertains to an eligible original ḍammah, not to final kasrah or fatḥah. It is chiefly observable visually rather than as an audible vowel.