がる

がる • (-garu) 

1. to behave or act as if feeling in a certain way

   恥(は)ずかしがらないで、前(まえ)に出(で)てきてください。

   Hazukashigaranai de, mae ni detekite kudasai.

   Please don't be shy (don't act all shy) and come up here.

   • 1928, Motojirō Kajii, Sakura no ki no shita ni wa‎, Modern kanji and kana edition:

     俺(おれ)を不(ふ)安(あん)がらせた神(しん)秘(ぴ)

     ore o fuan-garaseta shinpi

     mystery that made me anxious

2. to pretend

   今(いま)から強(つよ)がっても無駄(むだ)だ。

   Ima kara tsuyogatte mo muda da.

   There's no point in acting like a tough guy now.

This attaches to an adjective stem and creates a verb expressing a third party's feelings or a behavior that manifests such feelings. For example:

• 会(あ)いたい (aitai, “want to meet sb.”) → 会(あ)いたがる (aitagaru, “act as if wanting to meet sb.”)
• 重(ちょう)宝(ほう) (chōhō, “a treasure; convenient”) → 重(ちょう)宝(ほう)がる (chōhō-garu, “to value as a treasure; to value as convenient”)