Wordnet 3.0
ADJECTIVE (1)
1. 
 (of pitches) made with the arm moving parallel to the ground; 
- Example: "a sidearm pitch"ADVERB (1)
1. 
 in a sidearm manner; 
- Example: "he prefers to throw sidearm"
WordNet (r) 3.0 (2006):
sidearm
    adv 1: in a sidearm manner; "he prefers to throw sidearm"
    adj 1: (of pitches) made with the arm moving parallel to the
           ground; "a sidearm pitch"