っ

Small form of the hiragana character つ (tsu).

If preceding a consonant, results in the following consonant being geminate; an English example is cattail – see Gemination: English for further discussion.

If ending a word, results in the word ending in a glottal stop.

In no case is it pronounced like the full-size つ (tsu).

っ 

1. The そくおん (sokuon): a small form of つ (tsu). In romanization, this is represented by doubling the following consonant. The equivalent in katakana is ッ.

   いっぱい (ippai)

   もっと (motto)

   すっぱい (suppai)

   おっぱい (oppai)

   やってくる (yattekuru)

2. A glottal stop or “choked sound”.

   あ'っ！

   A''!

   Ah!

Primarily used as the sokuon (for gemination), which is a common sound. Used as a glottal stop at the end of interjections, primarily expressions of surprise or effort.

• (Hiragana) 平仮名; あぁ, いぃ, うぅゔ, えぇ, おぉ, かゕが, きぎ, くぐ, けゖげ, こ𛄲ご, さざ, しじ, すず, せぜ, そぞ, ただ, ちぢ, つっづ, てで, とど, な, に, ぬ, ね, の, はばぱ, ひびぴ, ふぶぷ, へべぺ, ほぼぽ, ま, み, む, め, も, やゃ, 𛀆, ゆゅ, 𛀁, よょ, らら゚, りり゚, るる゚, れれ゚, ろろ゚, わゎわ゙, ゐ𛅐ゐ゙, 𛄟, ゑ𛅑ゑ゙, を𛅒を゙, ん, ー, ゝ, ゞ, ゟ

っ 

1. (colloquial) very, super (inserted after the first syllable of an adjective, an adverb, or an ABAB-type onomatopoeia)

   でかい→でっかい

   dekai → dekkai

   huge → enormous!

   とても→とっても

   totemo → tottemo

   completely → totally!

   ぽかぽか→ぽっかぽか

   pokapoka → pokkapoka

   pleasantly warm → toasty warm

   あつあつ→あっつあつ

   atsuatsu → attsuatsu

   hot → super-hot