っぽい

っぽい goes straight onto a noun and means "-ish" or "-like": it gives that impression without really being it. It conjugates as an い-adjective (っぽくない, っぽかった, っぽく) and is conversational.

On a colour or on an い-adjective with い dropped, it means "-ish", often with a hint of cheapness.

On a ます-stem: "tends to"

After a ます-stem, っぽい describes a person who does that thing easily or too often. The list is short and the words are fixed: わすれっぽい忘れっぽい, おこりっぽい怒りっぽい, あきっぽい飽きっぽい, ほれっぽい惚れっぽい.

っぽい or らしい

On a noun, らしい means "has the qualities a real X should have", and っぽい means "seems like an X". So おとこ男らしい praises a man for being manly, while おとこっぽい男っぽい can describe anyone who comes across as masculine.

"Looks like" after a verb

In casual speech, っぽい also follows a plain-form verb and means "it looks like", much like みたい. This use is slangy; keep it out of writing and polite speech.