The most famous is the "Diccionario de la R.A.E" from the Royal Academy of Spanish Language but many people tend to favor the Maria Moliner's "Diccionario de uso del español" (usually known simply as "Maria Moliner") for its more detailed definitions.
If used for learning I would recommend the later. Also, you can always do a quick search in the RAE's web which has the same content as the physical "Diccionario de la R.A.E" book
The best Spanish dictionary for translations would be a English Spanish dictionary. It would then tell you Tal Vez means perhaps in English.
Spanish Dictionary, Google Translate, Translation Babylon, Free Translation, Free Translator, Translation Langenberg and My Spanish Dictionary all offer free Spanish to English Translation as well as several other languages.
CFA, CFP and CFM are all good degrees and the best for finance majors.
The Urban Dictionary definition for "perreando" is dirty dancing. It is a Spanish word and the exact definition will vary from place to place so it is best to look at multiple sources.
iJunoon online Urdu dictionary is best online Urdu dictionary
iJunoon online Punjabi dictionary is one of the best online Punjabi Dictionary
there is such a book as a Junior Dictionary
If English Dictionary, the English Dictionary by World Book is great.
h. Ramierez
UBC
The best English Farsi dictionary is Aryanpour English Farsi dcitionary
There is no such thing as the best major. Different majors are good for different purposes: no single major is good for everything. Also, different majors are good for different people..