The Collaborative International Dictionary of English v.0.48:

Megalerg \Meg"a*lerg\, n. [Megalo- + erg.] (Physics)
   A million ergs; a megerg.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Megerg \Meg"erg`\, n. [Mega- + erg.] (Physics)
   One of the larger measures of work, amounting to one million
   ergs; -- called also megalerg.
   [1913 Webster] Megilp