1. HEEDLESSLY.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• sisregardfully,
• xisregardfully,
• cisregardfully,
• fisregardfully,
• risregardfully,
• eisregardfully,
• dusregardfully,
• djsregardfully,
• dksregardfully,
• dosregardfully,
• d9sregardfully,
• d8sregardfully,
• diaregardfully,
• dizregardfully,
• dixregardfully,
• didregardfully,
• dieregardfully,
• diwregardfully,
• diseegardfully,
• disdegardfully

• disregard,
• yard,
• hard,
• lard,
• disregarded,
• bard,
• card,
• guard,
• TARD,
• regard.

The plural form of the word "disregardfully" is "disregardfully". The plural form remains the same as the singular form for this word.

The singular form of the word "Disregardfully" is "Disregardful"