/hɑ:; hɑ/
interj
1 (used to express surprise, joy, triumph, suspicion, etc 用以表示惊奇、快乐、得意、疑惑等)
2 (also ha! ha!) (used in print to indicate laughter; when spoken used ironically 书写或印刷中用以表示大笑声; 用于口头时含讥讽之意).

v (idm 习语) hum and ha => hum.

abbr 缩写 = hectare(s).

interjection
[Date: 1200-1300; Origin: A natural sound]
used when you are surprised or have discovered something interesting
　Ha! I thought it might be you hiding there!