The Patriots issued 14 walks, hit four batters and threw three wild pitches.
The Terps started 3-0, including a win over College of Charleston.
Flint leads the team through three games with six hits.
The Terps were behind 2-0 entering the ninth inning.
Dean struck out six and allowed two earned runs over 4 2/3 innings.
Sean Fisher struck out five in 5.1 innings in his first career start.
The Terps open the season Friday against Charleston Southern.
The No. 3 jersey symbolizes the Terps' three pillars of success.
Right-hander Elliot Zoellner pitched 3 1/3 scoreless innings of relief, but the Terps faltered late.