Princeton's WordNet

1. dad, dada, daddy, pa, papa, pappa, pop(noun)

   an informal term for a father; probably derived from baby talk

Kernerman English Learner's Dictionary

1. dad(noun)æd

   sb's father

   His dad is a police officer.; Can I take the car today, Dad?

Wiktionary

1. dad(Noun)

   A father, a male parent.

   He hadn't seen his dad in years.

2. Dad(ProperNoun)

   One's father.

   I will only do what Dad says.

Origin: From dadd, dadde, perhaps of origin, compare Welsh and Gaelic dad, tad; possibly related to Russian дядя.

Webster Dictionary

1. Dad(noun)

   father; -- a word sometimes used by children

• pa, pappaAfrikaans
• أب (بِلُغَةِ الأطْفال)Arabic
• таткоBulgarian
• papaiPortuguese (BR)
• tatínek, taťkaCzech
• der PapaGerman
• far; farmandDanish
• μπαμπάςGreek
• papáSpanish
• issiEstonian
• بابا؛ پدرFarsi
• isiFinnish
• papaFrench
• אַבָּאHebrew
• पिता, बापHindi
• tata, taticaCroatian
• papaHungarian
• papa, ayahIndonesian
• pabbiIcelandic
• babbo, papàItalian
• お父ちゃんJapanese
• 아빠Korean
• tėtis, tėvelisLithuanian
• tētis; tētuksLatvian
• ayahMalay
• papaDutch
• pappaNorwegian
• tataPolish
• بابا؛ پدرPersian
• پلارPashto
• papáPortuguese
• tăticRomanian
• папаRussian
• ocko, tatkoSlovak
• očkaSlovenian
• tataSerbian
• pappaSwedish
• พ่อThai
• babaTurkish
• 爸爸Chinese (Trad.)
• тато, татусьUkrainian
• باپ، اباUrdu
• cha, bốVietnamese
• 爸爸Chinese (Simp.)