• frubwork,
• vrubwork,
• brubwork,
• hrubwork,
• yrubwork,
• trubwork,
• geubwork,
• gdubwork,
• gfubwork,
• gtubwork,
• grubwirk,
• grubworkk,
• grubwerk,
• grubwark,
• grubberk,
• grabwork,
• grabwerk,
• grabwirk,
• grabwark,
• grabworkk

The adjective form of the word "grubwork" is "grubworkish".

The plural form of the word "grubwork" is "grubworks"

The singular form of the word "grubwork" is "grubwork". The word does not change in its singular form.