Hairspray is a sticky liquid you spray from a can onto finished hair so the style stays. You hold the can away from your head, spray a light cloud, and the hair feels a bit stiff and holds its shape — a bun, a wave, or hair that would otherwise go flat or fly up.

Hairspray is髮膠是 a sticky liquid一種黏黏的液體, you spray你把它 from a can從罐子裡噴出來 onto finished hair噴在已經弄好的頭髮上 so the style stays好讓髮型定住。You hold the can你把罐子拿 away from your head離頭稍微遠一點, spray a light cloud噴出一層薄薄的霧, and the hair feels a bit stiff頭髮會感覺有點硬硬的 and holds its shape並保持形狀 — a bun像丸子頭, a wave或波浪捲, or hair that would otherwise go flat or fly up或本來會塌掉或翹起來的頭髮。

People use it after they have already cut, dried, or set the hair; it is not shampoo and not the gel you work in with your fingers, though the job (keep hair still) is cousin to gel.

People use it大家會用它 after they have already cut, dried, or set the hair在頭髮已經剪好、吹乾或做好造型之後; it is not shampoo它不是洗髮精, and not the gel也不是那種gel（髮妝品） you work in with your fingers用手指抓進頭髮裡的, though the job雖然它的功能 (keep hair still讓頭髮固定不動) is cousin to gel跟gel很像。

It can feel old-fashioned or “stage and school photo,” but plenty of people still use it. Too much makes hair crunchy and white at the surface.

It can feel有時候感覺 old-fashioned old-fashioned（過時） or "stage and school photo"或像是「舞台和畢業照專用」, but plenty of people still use it不過還是有很多人在用。Too much太多的話 makes hair crunchy and white at the surface會讓頭髮變得脆脆的、表面泛白。

The word is everyday, not formal.

The word is everyday這個字是日常用語, not formal不是正式用語。