We regret to inform Twitter that welp is a word, even if it's not in the dictionary. Welp is a synonym of the interjection well, which is used to express surprise or signal the beginning of a comment or discussion ("Well, what have we here?" "Well, you're never going to believe this, but..."). But welp has a sense of resignation and finality that well often doesn't have
Source:Yes, 'Welp' Is a Real Word.
Welp also refers to a female dog having her puppies.