Does any skill have a global cooldown?

I am new to this game, and will try to optimize my game-play as much as possible. I will do this by making macros for my spells and abilities.

Are there global cooldown on spells and abilities in League of Legends?

Since this is important regarding macros to trigger spell and ability combos.

A Global Cooldown(GCD) is a cooldown which affect most if not all abilities, spells or items when using an ability, spell or item.

In most games it is there to prevent macroing/spamming of multiple instant abilities, spells or items, and usually has a set short duration independent of the ability, spell or items normal Cooldown.

Most champions do not have a cooldown of this nature, although there is a window while the ability is resolving (described as cast time on the wiki) where you can't do anything else, which may be what you're referring to.

There are exceptions to this however: Udyr has a global cooldown on stance-switch, Sona on song-switch, and Orianna has a short one after each ball ability.

The answers others have given are regarding the specific spells. What op is asking is if RIOT implements a global cooldown or "lockdown" i would put it.

The idea behind such Locks are to counter people that uses "bots" that exceed human reflex time.

To answer op's quesiton such kind of locks are not applied in League of legends (can't provide any source though). But a close inspection on each spells will tell you its not required. Every spell has either a cast time or a cool down, effectively limiting it from able to be spammed. Even if you hit the button at a faster rate than cast time it won't cast the spell twice.

There was a bug in League of Legends in which people could bring the cast time to negative value with a hack in client side, effectively making the spell spammable. But it was resolved.

Hope this helps you in writing the macro.