What is the legal definition of 'Aqiqah' (sacrifice for a newborn)?

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The 'Aqiqah' is the animal slaughtered on behalf of a newborn. Abu 'Ubayd suggested its origin relates to the hair removed from the newborn, as the plural is 'aqa'iq. Arabs later named the slaughter the 'aqiqah' upon shaving the hair, associating the name with the cause or proximity, which later became the conventional meaning, making the original literal meaning obscure; thus, when 'aqiqah' is used absolutely, only the slaughter is understood. This interpretation was rejected by Ahmad, who stated that 'aqiqah' is the slaughter itself, derived from the root meaning 'to cut,' as in cutting the throat, windpipe, esophagus, and jugular veins.