Abdul (also transliterated as Abdal, Abdel, Abdil, Abdol, Abdool, or Abdoul, Arabic: عبد ال, ʿAbd al-) is the primary transliteration of the Arabic compound words: Abd (عبد: "slave") and al / el (ال: "the").
It is a compound name, which means that it's a name made of two words. For example, عبد الحميد, ʿAbd el-Ḥamīd, ʿAbd al-Ḥamīd or ʿAbdu l-Ḥamīd, usually spelled Abdel Hamid, Abdelhamid, Abd El Hamid or Abdul Hamid.
The most common use for Abdul by far, is as part of a male given name, written in English. Understandably, when written in English, Abdul is subject to variable spacing, spelling, and hyphenation.
The meaning of Abdul literally and normally means "Slave of the", but in English translations some prefer to translate it to: "Servant of the".