Sentence:  ‘... If you're <WSD>dippy</WSD> about a girl, and another fellow has grabbed her, it can't be pleasant to sit at a writing table, probably with a rotten pen, sweating away while the other fellow dictates “My own comma precious darling period I worship you comma I adore you period How I wish comma my dearest comma that I could press you to my bosom and cover your lovely face with burning kisses exclamation mark”. ...' 
Meaning of the word marked with <WSD> tags:  Having romantic feelings for; excited or enthusiastic "about".